A 250 x 350 mm poly mailer at 40 microns works out at about 7 grams of film. A honeycomb paper envelope of about the same size typically weighs about 40. Per shipment, on the life cycle studies that compare the two directly, the plastic one usually has the smaller carbon footprint. The paper one is the one your customer can put in the recycling bin at home.
Both of those sentences are true. A choice made on only one of them is half a decision.
We supply both. Poly mailers, bubble mailers, honeycomb padded envelopes, rigid kraft mailers, glassine, honeycomb wrap, paper bubble wrap, void-fill paper, bottle sleeves, and a reusable mailer for brands that want the parcel to come back. So we have no reason to steer you to one material. This guide has a method instead: start with the product, then the route, then the market, then the claim you want to print. The material falls out of those four answers.
Under the EU Packaging and Packaging Waste Regulation, the paper you crumple into a half-empty box counts as empty space. The law names it: paper cuttings, air cushions, bubble wrap. From 2030 at the earliest, e-commerce packaging may be no more than 50% empty space, and void fill does not reduce that number. Only a smaller pack does.
What is e-commerce packaging?
E-commerce packaging is the packaging used to ship an online order to the customer’s door: an outer shipper (a poly mailer, bubble mailer, paper padded envelope, rigid board mailer or carton), protection inside it (wrap, cushioning, sleeves and void fill), and often an inner presentation layer such as a glassine or poly garment bag. Under EU law it is a kind of transport packaging, and from 2030 at the earliest it is subject to a 50% maximum empty space ratio, in which filling material counts as empty space. The right format is set by the product’s fragility, weight, shape and water sensitivity, by the carrier’s size and weight bands, and by the recycling system in the customer’s country. Bk-bags supplies e-commerce packaging in paper and in polyethylene (PE), from production in Vietnam and China, custom sized and printed, plus a reusable mailer programme, Pack it Forward, and has supplied retail clients worldwide since 2006.
Key Takeaways
- Choose by the product, not the material. Fragility, weight, water sensitivity and whether the item must stay flat decide the format. The material comes after.
- Per shipment, a light poly mailer usually beats paper on carbon. At about 250 x 350 mm a poly mailer is roughly 7 to 14 g of film and a typical honeycomb envelope about 40 g, and packaging weight is the biggest driver of the footprint. Paper wins on recycling at home and on litter.
- A kraft bubble mailer is paper on the outside and plastic on the inside. Bonded together, it goes in neither recycling bin as it is. If you want one material, ask what every layer is made of.
- Void fill is protection, not compliance. EU law counts paper fill, air cushions and bubble wrap as empty space. The 50% limit is met by right-sizing.
- Postage drops when the format changes, not when the grams do. A mailer that fits a large letter or flat band ships cheaper. A mailer that bulges by 5 mm can fall into the parcel rate.
- Ask whether your glassine is plain or waxed. Glassine gets its translucency from how the paper is made. Waxed glassine adds a wax coating for a stronger barrier, and wax is harder for standard paper mills to recycle. Ours is waxed, and that changes the recycling claim you can print on it.
- A reusable mailer is only as good as its return rate. At an 80% return rate the average bag makes 5 trips, whatever it was designed for. The loop decides the number, not the fabric.
- From 27 September 2026, “eco-friendly”, “green” and “biodegradable” are banned as generic claims in EU consumer marketing, packaging included, unless you can prove recognised excellent environmental performance or state the specific basis clearly on the same pack or page. Say the material, the percentage and the disposal route instead.
Contents
- The parcel, layer by layer
- Start with the product: a format for every job
- Poly mailers
- Bubble mailers, and the kraft bubble trap
- Honeycomb padded envelopes
- Rigid kraft mailers
- Protective paper: honeycomb wrap, paper bubble wrap, void fill and bottle sleeves
- Glassine: the paper garment bag
- Weight, size and postage
- Paper or plastic: what the life cycle studies found
- Reusable mailers and Pack it Forward
- The rules, now and to 2030
- What you can print on the mailer, and what you cannot
- Printing and branding
- Retail-ready packs for resellers
- Twenty-five questions to ask your packaging supplier
- FAQ
1. The parcel, layer by layer
Every parcel has up to five jobs to do, and each job can be done in paper, in plastic, or by the product’s own box.
| Layer | Its job | Plastic version | Paper version | Reusable version |
|---|---|---|---|---|
| Outer shipper | Survive sorting, rain, the letterbox | Poly mailer, co-ex mailer, bubble mailer | Honeycomb padded envelope, rigid kraft mailer, carton | Reusable zip mailer |
| Cushioning | Absorb drops and vibration | Bubble wrap, air pillows, bubble lining | Honeycomb wrap, paper bubble wrap, honeycomb core | Built into the mailer, or not needed for soft goods |
| Immobilising | Stop the product moving | Air pillows | Void-fill paper, bottle sleeves | Right-sized mailer |
| Presentation | Keep dust and handling off, look right when opened | Poly garment bag | Glassine envelope, tissue | |
| Closure and return | Seal, prove it was not opened, send it back | Adhesive strip, tamper-evident strip, double strip | Self-seal strip, tear strip, double strip | Zip plus return-label panel |
Most buyers specify the outer shipper and inherit everything else from whatever the warehouse already stocks. That is where the cost and the empty space hide. A parcel with a right-sized mailer and no void fill is lighter, cheaper to post and closer to the 2030 empty space rule than the same product in a box with paper stuffed around it.
“The question we ask first is not paper or plastic. It is what are you shipping, how far, and in what weather. A T-shirt, a perfume bottle and a print need three different answers, and a brand that ships all three from one box size is paying for air on two of them.”
Simmy Lin, Managing Director, Bk-bags
2. Start with the product: a format for every job
| What you ship | First choice | Paper alternative | Plastic alternative | Watch out for |
|---|---|---|---|---|
| Soft goods: apparel, textiles | Poly mailer, or honeycomb envelope | Honeycomb padded envelope, glassine inside | Poly or co-ex mailer, poly garment bag inside | Paper is heavier. Check the postage band |
| Small, semi-fragile: cosmetics, accessories, small electronics | Padded mailer | Honeycomb padded envelope, reinforced build | PE bubble mailer | Sharp corners puncture paper more easily |
| Must stay flat: prints, photos, documents, records, books | Rigid kraft mailer | Rigid kraft mailer | (none that stays flat) | Padded mailers cushion but do not stop bending |
| Glass: bottles, jars, candles | Carton with sleeves | Honeycomb bottle sleeve in a carton | Bubble wrap in a carton | A sleeve protects the bottle, the carton protects the sleeve |
| Fragile in a box: ceramics, glassware, gifts | Carton with wrap | Honeycomb wrap or paper bubble wrap | Bubble wrap, air pillows | More layers of paper than of bubble for the same job |
| Liquids, or wet routes | Poly or PE bubble mailer | Paper only with a tested water-resistant finish | Poly mailer | Plain paper is weak when wet |
| Returns-heavy categories | Mailer with a second adhesive strip | Double-strip honeycomb envelope | Returnable poly or bubble mailer | The return needs a closure, not tape |
| Repeat customers, short loops | Reusable mailer | The return rate decides whether it pays |
Sections 3 to 8 take each format in turn.
3. Poly mailers
The single-layer polyethylene mailer weighs a few grams, keeps rain and dust off the product, prints edge to edge, and costs less per unit than any other mailer in this guide.
What it is
A flat bag of low-density polyethylene (LDPE) film with a permanent adhesive strip under a release liner. Thickness is quoted in microns (µm). At 250 x 350 mm with a flap, the film alone works out at roughly 7 g at 40 µm, 10 g at 60 µm, 14 g at 80 µm and 21 g at 120 µm, plus a gram or two for the adhesive and liner. Those are calculated from film density. Weigh a sample of the mailer you are quoted.
The variants
| Type | What changes | Typical use |
|---|---|---|
| Standard poly mailer | Opaque white, grey or black film, 40 to 100 µm | Everyday apparel and soft goods |
| Apparel (frosted) mailer | Frosted or white film, 45 to 80 µm | Garments, where the look matters |
| Co-ex (co-extruded) mailer | Two or three layers extruded together, usually white outside and black or grey inside, for opacity | Anything the courier should not be able to read through |
| Security (tamper-evident) mailer | Aggressive permanent adhesive, destructible or “void” seal, sometimes serial numbers | High-value and confidential shipments |
| Returnable mailer | A second adhesive strip, so the customer reseals the same bag for the return | Apparel and any returns-heavy category |
| Wicket mailer | The same film, supplied on wickets for automatic bagging machines | High-volume fulfilment lines |
Our poly mailer range runs from 150 x 250 mm to 600 x 700 mm and from 40 to 120 µm, printed in up to eight colours.
Choose the thickness by the load, not by feel
Thicker film costs more, weighs more and, from 2030 at the earliest in the EU, needs more post-consumer recycled resin per mailer. A folded T-shirt does not need 100 µm. Heavy knitwear with sharp-cornered accessories inside might. Ask your supplier to match the gauge to the heaviest and sharpest thing you ship in that size, and to show you the puncture difference between two gauges on your own product.
Recycled content
Poly mailers with high recycled content exist and are certified, commonly up to 100% recycled, of which part is post-consumer. Three questions sort the real from the marketing:
- What percentage is post-consumer? “100% recycled” often combines post-consumer and post-industrial material.
- Which certificate covers it, and is it a scope certificate or a transaction certificate for your shipment? (Our GRS guide explains the difference.)
- Where is the recycled content going to be counted? The UK tax counts it one way, Spain another, and the EU from 2030 a third way (section 12).
Recyclability: depends where the mailer ends up
- UK: England’s mandatory kerbside collection of plastic film is being pushed back from March 2027 to April 2030. Wales is still going ahead in 2027. Until then, film recycling in England relies largely on supermarket drop-off.
- US: PE film is recycled through store drop-off, not curbside. How2Recycle removed the recycling arrows from its store drop-off label because of California’s labelling law, SB 343 (whose enforcement a federal court has since blocked, see section 12), and a poly mailer qualifies for that label only once the paper shipping label is removed.
- EU: mono-PE films are the format recyclers prefer, and collection varies country by country.
Within mono-PE, a plain white or light-coloured mailer sorts best. Dark colours are harder: optical sorters identify plastics by near-infrared light, and carbon black absorbs it. If you need opacity, ask for a grey or NIR-detectable black inner layer.
When plastic is the right answer
When the product is soft, the parcel is light, the route is wet, the budget is tight, or the mailer has to survive a long trip in an open truck. Plastic-free is a choice a brand can make product by product. It is not a rule that fits every SKU.
“We sell poly mailers and paper mailers, and sometimes I tell a client to keep the poly. If the product is liquid, or the parcel sits on a wet loading dock in the rainy season, paper is the wrong answer. The right answer is the lightest mailer that gets the product there intact, in a material the customer’s country can actually collect.”
Simmy Lin, Managing Director, Bk-bags
4. Bubble mailers, and the kraft bubble trap
A bubble mailer is a shell with a layer of air-bubble film bonded inside it. The bubbles absorb impact and vibration, which is why it is the standard mailer for electronics, cosmetics, small glass and anything with a screen.
| Shell | Build | Strength | Weakness |
|---|---|---|---|
| PE bubble mailer | PE film shell, PE bubble lining | Waterproof, light, low cost, one polymer family | Plastic, so the plastic rules apply |
| Kraft bubble mailer | Kraft paper shell, PE bubble lining bonded inside | Paper look on the outside | Two materials bonded together |
| Metallic bubble mailer | Metallised film shell, PE bubble lining | Premium look, gift unboxing | Hardest of the three to recycle |
Sizing is simple: allow about 2 cm of width on each side of the product, so the bubble layer wraps the edges, which is where impacts land.
The kraft bubble trap
A kraft bubble mailer is a plastic mailer in a paper coat. The shell is paper, the lining is polyethylene film, and the two are glued together. The American Forest and Paper Association’s guidance is that the paper has to be separated from the bubble lining before the paper can go in the recycling bin. Unpeeled, the bonded mailer goes in the general waste.
Amazon replaced almost all of its own mixed paper and plastic padded mailers in the US and Canada with paper-padded mailers in 2022 and 2023.
If you choose a kraft bubble mailer for the look, that is a legitimate choice. Just do not print a recycling claim on it, and do not describe it as paper packaging.
Metallic mailers
“Metallic” is a finish, not a material. Most metallic mailers are a metallised polyester (PET) or polypropylene film laminated to a PE bubble. The RecyClass design guidelines for PE films rate aluminium layers and non-PE polymers such as PET as not compatible with PE recycling, and metallisation as of limited compatibility. Buy it for the unboxing, not for the end of life, and ask the supplier what polymer the metallised film is.
5. Honeycomb padded envelopes
The all-paper padded mailer. Two walls of kraft paper with an expanded honeycomb paper core between them. The hexagonal cells absorb impact by crushing, and the whole envelope is paper.
Three builds
| Build | Structure | For |
|---|---|---|
| Standard (ABA) | Kraft, one honeycomb layer, kraft | Everyday soft and semi-fragile goods |
| Reinforced (ABBA) | Kraft, double honeycomb layer, kraft | Heavier or edge-sensitive goods |
| Super-sandwich (ABABA) | Alternating kraft and honeycomb | High-value and fragile mailings |
The cushioning core can also be pressed bubble paper for light goods at lower cost, or corrugated paper for heavier loads.
Sizes
Our seven stock sizes of honeycomb padded envelopes, each with a 45 mm self-seal flap:
| Size | Width x length | Fits |
|---|---|---|
| #1 | 150 x 210 mm | Phone accessories, cosmetic minis |
| #2 | 180 x 250 mm | Small electronics, jewellery boxes |
| #3 | 200 x 280 mm | A5 goods, books, spare parts |
| #4 | 220 x 310 mm | A4 documents, softcover books |
| #5 | 250 x 350 mm | Folded apparel, larger books |
| #6 | 300 x 400 mm | Knitwear, multi-item orders |
| #7 | 350 x 450 mm | Bulky apparel, small boxes |
Sizing a custom envelope. Width = product width + product thickness + 4 cm. Length = product length + product thickness + 2 cm. Then add 4.5 cm for the flap. When in doubt, size up, because a padded envelope that is too tight splits at the seam.
Closures and opening
A hot-melt self-seal strip under a release paper. A double-strip version seals twice, once for delivery and once for the return. A perforated tear line or a tear-off strip lets the customer open it without a knife, which matters when the knife would go through the product.
The honest limits
- It is heavier than a poly mailer. A typical honeycomb envelope of about 260 x 340 mm weighs around 40 g, against under 10 g of film for a light poly mailer of the same size. Section 9 explains when that matters for postage and when it does not.
- Plain paper is weak when wet. An optional water-resistant laminated finish exists. It changes the recycling story: a laminated paper mailer needs a recyclability test result before it can be called recyclable with paper, because a plastic lamination is exactly what paper mills test for.
- Sharp, heavy items puncture paper more easily than film. Use the reinforced build or a carton.
- Thickness eats into letter bands. The cushion layer adds millimetres. If you are aiming for a large letter rate, measure the filled envelope, not the empty one.
Recyclability, stated correctly
An all-paper honeycomb envelope with no lamination and no plastic window is designed to be recycled with household paper. Two details decide whether that holds. The adhesive: industry design guidance for paper recycling accepts hot-melt beads that soften above 68 °C and screen out in the mill, while pressure-sensitive peel-and-seal strips need a positive recyclability test. A self-seal strip under a release paper, ours included, is the pressure-sensitive kind. And the release liner: the strip you peel off is not part of the envelope and goes in the general waste. Ask your supplier for the recyclability test on the finished envelope, including the adhesive.
6. Rigid kraft mailers
Some things must arrive flat. Prints, photographs, certificates, vinyl records, calendars. A padded envelope cushions them. It does not stop them bending. A rigid mailer does.
Rigid kraft mailers are made from stiff paperboard, in our range 350 to 550 g/m² matched to the size and the content, with a self-seal strip and a perforated tear strip so nobody opens a print with a blade.
Common sizes run from 15 x 20 cm to 33 x 46 cm, including an A4-plus size of 24 x 32 cm, and custom. In the UK, every stock size up to 25 x 31 cm, plus the 24 x 32 cm, fits inside the Royal Mail Large Letter footprint of 353 x 250 mm, so each one posts at a letter rate as long as the filled mailer stays under 25 mm. That is the postage argument for a rigid mailer. In the US it does not work that way: USPS charges rigid pieces at package prices, so a rigid mailer does not get the flat rate.
The limit: a rigid mailer protects against bending, not against impact. A framed print or glass needs a carton.
7. Protective paper: honeycomb wrap, paper bubble wrap, void fill and bottle sleeves
These are the four paper products that replace the plastic inside a box. Each does a different job, and a packing station usually needs two of them, not all four.
| Product | What it does | Our spec | Replaces |
|---|---|---|---|
| Honeycomb packing paper | Wraps the product. Die-cut kraft that opens into a honeycomb mesh when pulled, and grips itself without tape | 80 g/m² kraft, rolls 30, 38 and 50 cm wide, 10 yd starter rolls to 250 m, pre-cut sheets 30 x 30 to 50 x 50 cm, dispenser cartons | Bubble wrap as a wrap |
| Paper bubble wrap | Wraps and separates. Kraft embossed with a double-sided bubble pattern, tear line every 30 cm | 80 g/m² kraft, 51 cm x 300 m rolls, sheets, fan-folded stacks | Bubble wrap between stacked items |
| Void-fill paper | Stops the product moving. Crumpled into the gaps | Fanfold and roll dispenser cartons, 30, 38 and 50 cm wide, 60 to 80 g/m², virgin or recycled kraft | Air pillows, loose fill |
| Honeycomb bottle sleeves | Grips and cushions a bottle or jar, and stops glass touching glass | Kraft with 1 cm cells, ships flat, 11, 22, 35 and 45 cm lengths, 50 to 80 g/m² | Bubble sleeves, foam and moulded inserts |
What paper cushioning can and cannot do
Paper protects by structure and layers, plastic by trapped air. For most e-commerce items, enough layers of honeycomb or bubble paper do the job. For heavy, very fragile or repeatedly dropped items, air cushioning still has an edge, and you will use more paper than you did bubble wrap. We have found no independent study that measures honeycomb paper against plastic bubble wrap under the same test, and we would be wary of any supplier who quotes you a percentage. The honest way to decide is to test your own product.
The tests to ask for are ISTA 3A, the general simulation for single parcels shipped through a parcel delivery system, which covers standard, small, flat and elongated packages, and for anything sold on Amazon, ISTA 6-Amazon.com-SIOC. A supplier who has run a drop test with your product inside can tell you how many layers you need. One who has not is guessing.
For void fill, Amazon has published a result. It said in 2024 that it had replaced 95% of the plastic air pillows in its North American deliveries with paper filler made from 100% recycled content, after independent lab testing found the paper gave the same or better protection. That test was air pillows against paper fill, not bubble wrap against honeycomb wrap.
Void fill is not an empty-space fix
Article 24 of the Packaging and Packaging Waste Regulation sets a maximum empty space ratio of 50% for e-commerce packaging, and says in terms that space filled by “paper cuttings, air cushions, bubble wraps” and other filling materials “shall be considered as empty space”. A box half full of product and half full of crumpled paper sits exactly at the limit.
So void fill keeps the product from moving, and right-sizing keeps you inside the law. The compliant answer is a smaller box, or a mailer that takes the shape of the product, with just enough void fill for protection. A retail survey for DS Smith found 34% of retail business leaders admitted that the parcels they ship are at least double the size of the product. Those are the parcels the 2030 rule is written for.
“Paper cushioning works by layers. Buyers who swap one layer of bubble wrap for one layer of honeycomb paper and then see breakage blame the paper. The fix is to test the product and count the layers, and to cut the box down so there is less space to fill in the first place.”
Simmy Lin, Managing Director, Bk-bags
8. Glassine: the paper garment bag
Glassine is a smooth, translucent paper. Its translucency, density and resistance to grease and dust come from how it is made: the pulp is heavily refined and the dried sheet is supercalendered, pressed between polished rolls until the fibres close up.
It comes in two versions. Plain glassine is the paper as it leaves the calender, with no coating. Waxed glassine has a wax coating on top, which gives a stronger barrier against moisture and grease and a slightly softer, more translucent finish.
Our glassine envelopes are waxed glassine. We say so because the wax changes the end of life. The European paper industry’s design guidance lists waxed papers among the special grades that need specialised recycling mills, and warns that wax coatings can cause sticky deposits and clog screens at a standard mill. So a waxed glassine envelope is paper-based and contains no plastic film, but it should not carry an unqualified “recycle with paper” claim. If the recycling message on your packaging matters more to you than the barrier, ask for plain glassine instead.
Whoever you buy from, ask which version it is and, if it is waxed, which wax: paraffin, which is petroleum-based, or a plant or beeswax. Both answers change what you can claim on it.
Where it is used
As the inner layer that replaces the poly garment bag: folded T-shirts and knitwear, art prints, greeting cards, stickers, small accessories. The product shows through, and the customer knows what it is before touching it.
What it does not do
It is inner packaging. It protects against dust, grease and handling inside a shipper, not against rain, sorting machines or the letterbox. Pair it with an outer mailer.
Food contact
If you use glassine or any grease-resistant paper in contact with food, the EU limits on PFAS in food-contact packaging have applied since 12 August 2026: 25 parts per billion for any single PFAS, 250 ppb for the sum of targeted PFAS, and 50 parts per million for total PFAS. Glassine normally gets its grease resistance from density and, when waxed, from the wax, not from fluorochemicals, but some greaseproof papers historically used PFAS, and only a lab result proves it for a given paper. Ask for a PFAS declaration or a total fluorine test. For apparel and prints, the PFAS limits do not apply.
9. Weight, size and postage
“Lighter, so postage drops” is half true. What drops the price is usually the format, not the grams.
The bands that matter
| Carrier | Rule | Limit |
|---|---|---|
| Royal Mail (UK) | Large Letter | Max 353 x 250 x 25 mm and 750 g |
| USPS (US) | Flat (large envelope) | Max 15 x 12 in and 3/4 in thick, 13 oz for First-Class Mail. Must be flexible: rigid pieces pay package prices |
| UPS and FedEx | Dimensional weight | Length x width x height in inches ÷ 139 on account rates (166 at the retail counter), each dimension rounded up to the next whole inch, billed in whole pounds, on mailers as well as boxes |
| DHL Express | Volumetric weight | Length x width x height in cm ÷ 5,000 = kg |
| USPS | Dimensional weight | Only above 1 cubic foot |
What that means in practice
- The letter band is where the saving is. A mailer that ships as a Royal Mail Large Letter or a USPS flat is priced as a letter, not a parcel. Thickness, not weight, is what most mailers fail: a padded envelope with a bulky product in it can easily pass 25 mm. Measure the filled mailer.
- With UPS and FedEx, grams rarely matter for light parcels. They bill in whole pounds and apply dimensional weight to every package. On account rates, a 14 x 10 x 1 inch mailer is 140 cubic inches, which divided by 139 rounds up to 2 lb billable, whether it weighs 50 g or 500 g. Cutting a few grams of paper changes nothing. Cutting an inch of thickness can drop a whole pound.
- Against a box, any mailer wins. The published studies put a corrugated apparel box at around 200 g and larger boxes far above that. Swapping a box for a mailer, where the product allows it, is the biggest postage and carbon saving in this guide.
“Paper is heavier than film for the same protection. On a light parcel that can push you into the next postage band, and the buyers who skip that step find out on the first invoice. Weigh and measure a filled sample before you order a container.”
Simmy Lin, Managing Director, Bk-bags
10. Paper or plastic: what the life cycle studies found
Per shipment, the light plastic mailer usually has the lower carbon footprint. Every study we found that compared mailers directly agrees, because the plastic mailer is several times lighter and packaging weight is the biggest single driver.
| Study | What it compared | What it found |
|---|---|---|
| Franklin Associates for Oregon DEQ, US EPA and Metro (2004, peer reviewed) | Mailers and boxes for mail-order soft goods | The weight of the packaging is “the most critical factor”. Per package, on our conversion of the study’s tables: roughly 111 g CO2e for an unpadded plastic film bag, 226 g for an unpadded bleached kraft bag, 369 g for a kraft bag padded with shredded newspaper, and 1.6 to 2.1 kg for a box with dunnage |
| Oregon DEQ meta-analysis (2018) | Over 520 comparisons across the LCA literature | Recyclable packaging had higher impacts in 44% of comparisons and lower in 39%. Compostable packaging had lower impacts only 31% of the time |
| Virginia Tech research (Kim and Russell, 2021) | Apparel e-commerce packaging | A corrugated box had about 3.5 times the carbon of a paper envelope and 4.4 times that of a recycled LDPE bag. The paper envelope was modelled with a much longer supply route |
The 2004 study is old, and it did not include methane from paper breaking down in landfill, which would widen the gap against paper rather than close it.
So why would anyone choose paper? Because carbon is one measure, not the only one.
- Recycling at home. Paper is collected at the kerbside across most of Europe, the UK and the US. Film mostly is not, yet.
- Litter and leakage. Paper fibre does not persist in the environment the way plastic film does.
- Plastic taxes and targets. Paper is outside the UK Plastic Packaging Tax, the Spanish plastic packaging tax and the EU’s recycled-content targets for plastic.
And why would anyone choose neither? Because the biggest carbon saving is not the material. It is replacing a box with a mailer, and replacing an oversized box with a right-sized one. On our reading of the Oregon data, a mailer has roughly a quarter to a twentieth of the footprint of a box.
The sentence we would print, if we had to print one: choose the lightest format that protects the product, in a material your customer’s country can collect. “Paper has a lower carbon footprint” is not a sentence the studies above support.
11. Reusable mailers and Pack it Forward
A reusable mailer is the one format in this guide designed to be used more than once. Pack it Forward is our reusable mailer programme: a water-resistant laminated shell in woven polypropylene (PP) or recycled PET (rPET) non-woven, a heavy-duty zip, and a return-label panel on the flap, so the customer folds the empty bag flat, sticks the label and posts it back. The brand owns the bags, and decides how the loop closes: a prepaid return label, drop-off in store, or pickup with the next delivery.
The number that decides everything: the return rate
A reusable bag is built for many trips, and the parts that wear out are the zip, the seams and the label panel. But how many trips it actually makes is set by how many come back, not by the fabric. If a share r of bags return after each trip, the average bag makes 1 ÷ (1 − r) trips before it is lost:
| Return rate | Average trips per bag |
|---|---|
| 70% | 3.3 |
| 80% | 5 |
| 90% | 10 |
| 95% | 20 |
| 98% | 50 |
That table is arithmetic, not a claim about any programme. Ask for it in any reuse pitch. A bag built for 50 trips in a loop with an 80% return rate averages five.
When reuse wins on carbon, and when it does not
The peer-reviewed studies agree on the direction and disagree on the number, because the number depends on what you compare against and how far the empty bag travels.
| Study | Reusable mailer | Break-even against |
|---|---|---|
| Zimmermann and Bliklen, GAIA (2020) | 118 g polypropylene bag, returned 2,000 km by post | A carton: from the first trip. A 30 g virgin plastic mailer: about 8 trips, or about 3 if the reusable bag is made from recycled plastic. A mailer with 80% recycled content: about 20 trips |
| Zimmermann and Hauschke, Sustainability (2024), using data from the German reusable packaging provider hey circle | 82 g reusable bag | A plastic mailer: about 3 trips. A paper mailer: 8 to 9. A carton: 1 |
| Park et al., Journal of Industrial Ecology (2024) | Returnable mailer sent back to a distant central hub | Did worse than a 17 g plastic mailer in 9 of 10 impact categories, even at 40 trips |
Read together, reuse beats a box almost immediately, beats a light plastic mailer only after several trips, and can lose to it altogether if the empty bag travels a long way to come home. The 2020 authors also noted that no reusable system on the market was cheaper than single-use.
The conditions that make reuse work are the same in every study: a light bag, ideally made from recycled material, a short trip home, a return rate near or above 90%, and an empty return that travels as a letter, not a parcel.
Why the bag folds to letter size
The empty return is where reusable programmes lose money. Tchibo, the best-documented pilot in Europe, stopped for this reason: sending the empty bags back was not yet economic.
So a Pack it Forward bag is designed to fold flat inside the large letter limits, because at letter rates the numbers change:
| Market | Letter-rate return for an empty folded bag | Size limit |
|---|---|---|
| US | First-Class flat: $1.69 (1 oz), $1.98 (2 oz), $2.27 (3 oz). With a Business Reply Mail permit ($390 a year) you pay only for the bags that come back, plus a per-piece fee of $1.31, or $0.164 on a high-volume account with a $1,130 annual fee | 15 x 12 x 3/4 in, must stay flexible and even in thickness |
| UK | Second-class large letter up to 100 g: £1.55 | 353 x 250 x 25 mm |
| Germany | Großbrief: €1.80 | 353 x 250 x 20 mm, up to 500 g |
That constraint sets the fabric weight, the zip and the size range. A heavier fabric is more durable and can push the folded bag over the weight band or the thickness limit, and then every return is charged as a parcel.
What the pilots actually showed
The best-documented consumer trial in Europe is Tchibo’s. Between 2023 and 2024 it sent 26,000 of its own reusable bags to randomly selected customers, with no deposit and no incentive, and about 80% came back. The bags still averaged only 3 trips in the pilot, below the 4 trips Tchibo calculated it needed to break even on CO2, and Tchibo stopped the scheme in December 2024 because returning the empty bags was not yet economic. Otto’s 2020 pilot was reported at a 75% return rate. Zalando, after two pilots in the Nordics, said that “only a small amount of the packaging came back”, did not scale it, and moved reuse into its own warehouse network instead.
The published pilots and surveys show three patterns:
- Customers who choose reuse return it far more often than customers who are sent a reusable bag without asking for it.
- An incentive changes the number. A deposit, a discount on the next order, or a penalty for not returning.
- Surveys overstate it. In Macfarlane Packaging’s 2025 Unboxing Survey, 84% of shoppers said they would send reusable packaging back, “but only if retailers cover the cost of the return”. Observed returns from randomly selected customers run lower.
Where reuse fits, and where it does not
It fits subscription, rental and repeat-purchase brands, where the next delivery can collect the last bag. Apparel with frequent returns, where the product return travels back in the same bag: in the US, retailers expected 19.3% of 2025 online sales to be returned. B2B deliveries between the same sites. Any brand with stores where customers can drop the bag. And any programme where the customer opts in, rather than being sent a reusable bag by default.
It does not fit one-off purchases to customers you will never ship to again, products that need rigid protection, or a brand not prepared to run the returns: tracking bags, cleaning them, and replacing the lost ones.
What the law says about reuse
Three points from the EU regulation:
- No EU rule forces online sellers to ship business-to-consumer parcels in reusable packaging. The 40% reuse target for transport packaging from 2030 covers a listed set of formats, exempts cardboard boxes entirely, and exempts micro-enterprises placing 1,000 kg or less. The 100% targets apply only to deliveries between businesses in the same EU country and between a company’s own sites. The only general duty to offer consumers a reusable option falls on take-away food and drink.
- Reusable packaging used within a re-use system is exempt from the 50% empty space limit. That is a genuine advantage for a reusable mailer, provided there is a real system behind it.
- “Reusable” is a legal category, not an adjective. Under the regulation, packaging is reusable only if it is designed for multiple rotations, can be reconditioned, is recyclable at the end of its life, and sits inside a re-use system with an incentive to return it. The Commission is due to set minimum rotation numbers by February 2027. From 12 August 2026, anyone who first places reusable packaging on the EU market must make sure such a system exists.
“If you know who your customers are, how many bags come back and how the empty bag gets home, we can build a bag for that loop and tell you how many trips it needs to beat the mailer you use now. If you do not know those three things yet, start with a double-strip mailer and find out.”
Simmy Lin, Managing Director, Bk-bags
12. The rules, now and to 2030
European Union: the Packaging and Packaging Waste Regulation (EU) 2025/40
The regulation has applied since 12 August 2026. That date started the rulebook, not the big design rules, which come later.
| Date | What applies | Who carries it |
|---|---|---|
| 12 Aug 2026 | PFAS limits for food-contact packaging. Heavy metal limits for all packaging. Technical documentation and declaration of conformity. EPR registration in each country where packaging is first made available. Online platforms and fulfilment providers must check sellers’ EPR registration. Re-use system obligations for anyone using reusable packaging | Manufacturers, importers, producers, platforms |
| 27 Sep 2026 | Ban on generic environmental claims to consumers (Directive (EU) 2024/825, see section 13) | Whoever makes the claim |
| Feb 2027 | Minimum rotations for reusable packaging due from the Commission | |
| 12 Aug 2028 at the earliest | Harmonised material-composition label for sorting. E-commerce packaging must carry it, even though other transport packaging need not. The Commission missed its August 2026 deadline for the label design, so the real date will be later | Brand or producer |
| 1 Jan 2030 at the earliest | Maximum 50% empty space for e-commerce packaging, with filling material counted as empty space. Applies from 1 January 2030 or three years after the calculation method is adopted, whichever is later | Whoever fills the packaging: the seller or its fulfilment provider |
| 1 Jan 2030 | Packaging must be minimised in weight and volume. No false bottoms, double walls or unnecessary layers | Manufacturer or importer |
| 1 Jan 2030 at the earliest | Every pack must reach recyclability grade C or better (at least 70% recyclable by weight). Grade C is dropped from 2038 | Manufacturer or importer |
| 1 Jan 2030 at the earliest | 35% post-consumer recycled content in plastic packaging such as poly mailers, rising to 65% in 2040. Paper has no recycled-content target. A plastic part under 5% of the pack’s weight is excluded | Manufacturer or importer |
Four things buyers get wrong.
- Nobody can certify a mailer as “PPWR grade A” today. The design-for-recycling criteria per material come in delegated acts due by 1 January 2028. Anything labelled with a grade now is a self-assessment against industry guidelines.
- The empty space rule falls on the seller, the minimisation rule on the maker. If you import unbranded mailers into the EU from Asia, you are the importer, and the minimisation documentation is yours.
- The recycled content rule counts post-consumer material only, averaged per manufacturing plant per year. Recycled content produced outside the EU counts only under equivalence rules the Commission is still writing.
- A compostable plastic mailer is not an exit. From February 2028, all packaging outside a short list, including biodegradable plastic packaging, must be designed for material recycling.
Germany and Spain
- Germany replaced its Packaging Act (VerpackG) with the VerpackDG on 12 August 2026. Producers must register with the central packaging register before selling, join a dual system for packaging that ends up in households (which includes e-commerce shipping packaging), and sellers based outside Germany must now appoint an authorised representative. Fulfilment providers may not pack or ship for an unregistered producer.
- Spain taxes non-reusable plastic packaging at €0.45 per kg of non-recycled plastic, including imported empty poly mailers and plastic packaging arriving around goods, above 5 kg a month. Certified recycled plastic is deducted kilo for kilo. A paper padded mailer is taxed only on the plastic it contains.
United Kingdom
- Plastic Packaging Tax: £228.82 per tonne from 1 April 2026, on plastic packaging with less than 30% recycled plastic, for businesses that make or import 10 tonnes or more a year. It applies to imported unfilled poly mailers. A multi-material item counts as plastic only if plastic is its heaviest material, so a paper padded envelope usually falls outside.
- Extended producer responsibility (pEPR): producers of household packaging pay disposal fees, and e-commerce mailers end up in households. 2025 base fees were £196 per tonne for paper and card and £423 for plastic. From 2026/27 fees are modulated by recyclability: red-rated packaging pays 1.2 times the amber rate, rising to 2 times by 2028/29. A UK warehouse or even a UK returns address can make an overseas seller “established in the UK” and obligated.
United States
Seven states have packaging extended producer responsibility laws: Maine, Oregon, Colorado, California, Minnesota, Maryland and Washington. The detail most buyers miss is who the producer is. For the shipping mailer, it is usually whoever packs and ships the order to the consumer, not the mailer’s maker and not always the brand. Oregon, Maine and Minnesota say so in their statutes, and Washington and California’s regulations take the same approach. Paper mailers and void fill are covered too. Paper is not exempt from EPR, it is just cheaper under it.
| State | Where it stands in 2026 |
|---|---|
| Oregon | Running since 1 July 2025, fees live. Upheld in full by the US District Court for Oregon in August 2026. An appeal is possible |
| Colorado | Producer fees payable from January 2026 |
| California (SB 54) | Regulations in force since 1 May 2026. Producers had to register by 1 June 2026. Full programme from 1 January 2027, when unregistered producers can no longer sell covered material into the state. Plastic packaging must be cut 25% by 2032 against 2023, and all covered packaging, paper included, must be recyclable or compostable by 2032 |
| Maryland, Washington | Registration deadlines passed in mid-2026. Sales bans for non-compliant producers from 2028 and 2029 |
| Minnesota | Law in place. First stewardship plan and fees still ahead, with producer costs phased in from 2029 |
| Maine | Law in place. The state’s call for a stewardship organisation closed in August 2026 with no bids, so no fees yet |
California’s recycling label law (SB 343) restricts the recycling symbol and the word “recyclable” to materials that are collected by programmes serving at least 60% of Californians and sorted in facilities serving at least 60% of the state’s counties. CalRecycle’s study puts corrugated board and kraft paper comfortably above both lines. Plastic film, and the category “mailing pouches and shipping envelopes”, sit far below them. The restrictions were due to apply to packaging manufactured after 4 October 2026, but on 14 July 2026 a federal court blocked the state from enforcing the law while the case continues. The law itself still stands, and its definition of recyclable is the one California’s EPR programme uses for its 2032 target.
The FTC Green Guides still date from 2012. They say a “recyclable” claim needs facilities available to at least 60% of consumers or communities, or it must be qualified, and that an unqualified “biodegradable” is deceptive for anything customarily landfilled, incinerated or recycled.
“Sellers ask us whether Europe is going to force them into reusable parcels. It is not. What it will ask for is paperwork: what each layer is made of, what it weighs, and how much of the box is air.”
Simmy Lin, Managing Director, Bk-bags
13. What you can print on the mailer, and what you cannot
From 27 September 2026, EU consumer law bans generic environmental claims that the trader cannot back with recognised excellent environmental performance, meaning the EU Ecolabel or an officially recognised ecolabel. The directive’s own examples include “environmentally friendly”, “eco-friendly”, “green”, “ecological”, “climate friendly” and “biodegradable”. A claim stops being generic only if the specific basis is stated clearly on the same medium. It also bans environmental claims about the whole product when they are only true of part of it, and sustainability labels not based on a certification scheme.
In the US, the tests for “biodegradable”, “recyclable” and the recycling symbol are the FTC Green Guides and California’s SB 343, both covered in section 12.
What you can say, where it is true
- “Paper. Recycle with paper where collected.” On an all-paper mailer with a tested adhesive.
- “Made with X% post-consumer recycled plastic”, where X comes from the certificate for those goods.
- “Plastic-free”, only if the whole item is: shell, cushioning, adhesive, coating, window and ink. A paper mailer with a plastic lamination or film window is not plastic-free.
- “Reusable. Return in any postbox.” On a reusable mailer that sits inside a real return system.
- “FSC® Mix” or another FSC claim, with the licence code next to it, on paper covered by the supplier’s FSC certificate and the claim on your invoice. Our FSC guide explains why an FSC Mix Credit product may contain no certified fibre at all.
What you cannot say
- “Eco-friendly”, “green”, “sustainable”, “eco mailer” as free-standing claims.
- “Biodegradable” on a mailer. It is on the directive’s list of generic claims, and a mailer with an adhesive strip and release liner is not wholly paper anyway.
- “Compostable” without the standard, for example EN 13432 for industrial composting, and, once the EU label rules apply (August 2028 at the earliest, and later in practice), without the words that say it is not for home composting.
- “Recyclable” on a kraft bubble or metallic mailer, or with the chasing arrows on a PE mailer sold into California unless it meets SB 343.
- “100% recyclable” on anything. Say what it is made of and where it goes.
“The safest claim is the boring one: the material, the percentage, where it goes after use. Every adjective you add is one more thing a regulator can ask you to prove.”
Simmy Lin, Managing Director, Bk-bags
14. Printing and branding
| Format | Print method | Colours | Notes |
|---|---|---|---|
| Poly and bubble mailers | Flexography on film | Up to 8 | Edge-to-edge print |
| Honeycomb envelopes, rigid mailers | Flexography on kraft or white paper, water-based inks | One-colour logo to full surface | White paper gives the cleanest print. Brown kraft gives the natural look and darker, less saturated colours |
| Glassine | Logo or full design | Crisp on the smooth surface. Translucency means print shows from both sides | |
| Honeycomb and bubble paper, void fill | Printed dispenser cartons. The paper itself can be dyed | Brown, white, red, black, pink, blue, custom | Colour dyed through the paper keeps its shade when the honeycomb expands |
Three practical points. Leave space in the artwork for the EU sorting label, which e-commerce packaging must carry once it applies. Put the return instruction on returnable mailers in words and icons, because the customer reads it once. And print the size on the mailer, so the packing station stops guessing.
15. Retail-ready packs for resellers
The second buyer of e-commerce packaging is the shop that sells it: stationery stores, post office shops, packaging distributors. For them the pack is the product.
We supply the e-commerce packaging range in retail formats: counted packs of poly mailers in 25, 50 and 100, window boxes and belly-band packs of honeycomb envelopes, 30-piece display cartons, bottle sleeves in window boxes, hang boxes, canisters and tubes, honeycomb paper in boxed rolls, dispenser cartons and sheet packs, and rigid mailers in shrink-wrapped or boxed packs of 10, 25 and 50. Every format can carry the reseller’s own brand, barcode and sizes.
16. Twenty-five questions to ask your packaging supplier
Copy this into your RFQ. Ask for the answers in writing.
The product and the format
- Which format do you recommend for this product, and why not the alternatives?
- What is the weight of one empty mailer in this size, and what is its flat thickness?
- Filled with my product, does it stay inside the large letter or flat limit for my carrier?
- Which film gauge or paper build do you recommend for my heaviest and sharpest item in this size?
- Has this format been drop-tested with a product like mine, to ISTA 3A or ISTA 6-Amazon? Can I see the report?
Materials, layer by layer
- What is every layer made of: shell, cushioning, adhesive, release liner, coating, ink?
- For paper items: virgin or recycled fibre, which grammage, and is there any lamination or coating?
- For glassine: plain or waxed, and if waxed, which wax?
- For plastic items: what percentage is post-consumer recycled, and which certificate covers my shipment?
- For co-ex mailers: what colour is the inner layer, and is it detectable by near-infrared sorting?
- For metallic mailers: what is the metallised film made of?
Recycling and claims
- Has the finished item, including the adhesive, been tested for paper recyclability? Which method?
- What exactly may I print about recycling on it, in each of my markets?
- If the item is FSC, what is the licence code, what is the claim, and will it appear on my invoice?
- For food contact: can you supply a PFAS declaration or a total fluorine test?
Regulation
- What does one unit weigh by material, so I can report EPR and plastic tax?
- Who will be the importer of record in the EU or UK, and who holds the technical documentation?
- Will the artwork leave room for the EU sorting label?
- For UK Plastic Packaging Tax: is the recycled content 30% or more, with evidence?
Returns and reuse
- Is there a double-strip version for returns?
- For a reusable mailer: how many trips is it designed for, and how was that tested?
- Does the empty reusable mailer fold inside the large letter limit?
- What does the return loop need from me: labels, a postal permit, a cleaning step, spare bags?
Order and supply
- What are the minimum order, the lead time and the sample time for this item, printed?
- Can you pack it retail-ready, with my barcode, if I resell it?
Send the list with your first RFQ. We will answer it too.
17. FAQ
Should I choose paper or poly mailers? Choose by the product and the market. Poly mailers are lighter, waterproof and cheaper per unit, and per shipment usually have the lower carbon footprint. Paper mailers are collected for recycling at the kerbside in most of Europe, the UK and the US, and fall outside plastic taxes and plastic recycled-content rules. For soft goods on dry routes either works. For liquids and wet routes, use poly. You can also run both: poly for those, paper for the rest.
Are paper mailers better for the environment than plastic mailers? Not on carbon per shipment, on the studies that compare them directly. A paper mailer is several times heavier, and packaging weight is the biggest driver of its footprint. Paper’s advantages are recycling at home and lower litter persistence. The biggest saving of all is shipping in a mailer instead of a box, and in a right-sized pack instead of an oversized one.
Are kraft bubble mailers recyclable? Not as they are. The paper shell is bonded to a polyethylene bubble lining, and the paper industry’s guidance is that the two must be separated before the paper can be recycled. Unseparated, the mailer goes in the general waste. For a mailer that goes straight into paper recycling, use an all-paper padded envelope with a honeycomb or paper cushioning core.
Are honeycomb padded envelopes recyclable? An all-paper honeycomb envelope with no lamination or plastic window is designed to be recycled with household paper. Confirm two details with the supplier: that the self-seal adhesive has passed a paper recyclability test, and that there is no water-resistant lamination. The release liner you peel off the strip goes in the general waste.
Is glassine plastic? Is it waxed? Glassine is not plastic. It is paper that has been heavily refined and supercalendered, which makes it smooth, dense and translucent. It is sold plain or waxed. Waxed glassine, which is what Bk-bags supplies, has a wax coating for a stronger moisture and grease barrier, and waxed papers need specialised recycling mills, so it should not carry an unqualified paper recycling claim. Both versions are used in place of the poly garment bag.
Does void-fill paper help meet the EU 50% empty space rule? No. The regulation counts space filled by paper cuttings, air cushions, bubble wrap and other filling materials as empty space. The limit applies to e-commerce packaging from 1 January 2030 at the earliest and is met by using a smaller pack or a mailer that fits the product. Void fill is there to stop the product moving, not to reduce the ratio.
Do paper mailers cost more to ship? Sometimes. With letter-based services, the question is whether the filled mailer stays inside the large letter or flat limits, where thickness matters more than weight. With UPS and FedEx, light parcels are billed in whole pounds and by dimensional weight, so a few extra grams rarely change the price but an extra inch of thickness can. Measure a filled sample before ordering.
Do online sellers have to use reusable packaging in the EU? No. The EU’s reuse targets for transport packaging exempt cardboard boxes, apply 100% only to deliveries between businesses in the same EU country and between a company’s own sites, and do not require consumer parcels to be reusable. Reusable packaging used within a re-use system is exempt from the 50% empty space limit, which is a real advantage but not an obligation.
How many times can a reusable mailer be used? As many times as it comes back. The bag’s design rating sets the ceiling, and the return rate sets the average: at an 80% return rate the average bag makes 5 trips, at 90% it makes 10, and 50 trips needs a return rate of about 98%. Plan a reusable programme around the return rate you can realistically achieve.
Can I call my mailers eco-friendly? Not in consumer-facing EU marketing from 27 September 2026, unless the product holds the EU Ecolabel or an equivalent recognised ecolabel, or you state the specific basis clearly on the same pack or page. Simpler: state the fact instead: the material, the recycled percentage and the disposal route.
Do poly mailers need recycled content? In the EU, plastic packaging needs 35% post-consumer recycled content from 1 January 2030 at the earliest. In the UK, plastic packaging with less than 30% recycled plastic pays Plastic Packaging Tax of £228.82 per tonne from April 2026. In Spain, non-recycled plastic in packaging is taxed at €0.45 per kg. Ask for the post-consumer percentage and the certificate that covers your shipment.
Can Bk-bags print my logo on e-commerce packaging? Yes. Poly and bubble mailers print in up to eight colours, paper mailers from a one-colour logo to full-surface designs with water-based inks, and dispenser cartons, retail packs and glassine can all carry your branding. Every item is available in standard or custom sizes.
Talk to us with your product in your hand
Tell us what you ship, how far, and where your customers are. We will tell you which format we would use, what it weighs, what it costs to post, and what you can print on it, including when the answer is the mailer you already have.
Request a benchmark · E-commerce packaging range · Pack it Forward · FSC guide
About the author
Simmy Lin is Managing Director at Bk-bags, a supplier and developer of reusable shopping bags and e-commerce packaging with production in Vietnam and China. Bk-bags has supplied retail clients worldwide since 2006, and holds GRS and FSC® chain-of-custody certificates (FSC® C232146) and is BSCI audited.
Sources: Regulation (EU) 2025/40 on packaging and packaging waste, Articles 5, 6, 7, 9, 10, 11, 12, 24, 25, 26, 29 and Annexes II and V; European Commission, Guidance document for Regulation (EU) 2025/40, C/2026/3084; DG ENV, PPWR Frequently Asked Questions (August 2026); Directive (EU) 2024/825; Verpackungsrecht-Durchführungsgesetz, BGBl. 2026 I Nr. 207; Spain, Ley 7/2022, Articles 68 to 78; HMRC, Plastic Packaging Tax guidance (2026); Defra and PackUK, extended producer responsibility for packaging, fees and modulation statement (2025 to 2026); US FTC Green Guides, 16 CFR Part 260; California SB 343; Franklin Associates for Oregon DEQ, Life Cycle Inventory of Packaging Options for Shipment of Retail Mail-Order Soft Goods (2004); Oregon DEQ, packaging attributes meta-analysis (2018); Kim and Russell, Virginia Tech (2021); American Forest and Paper Association, How do I recycle paper padded mailers (2022); Cepi, Paper-based Packaging Recyclability Guidelines; 4evergreen, Circularity by Design Guideline v3 (2026); RecyClass, Design for Recycling Guidelines for coloured PE films (2026); ISTA 3A and ISTA 6-Amazon.com-SIOC; Amazon sustainability reports 2024 and 2025; DS Smith, Empty Space Economy (2018); Royal Mail, USPS, UPS, FedEx, DHL and Deutsche Post published size, price and dimensional weight rules (USPS Notice 123, July 2026); Zimmermann and Bliklen, GAIA 29(3) (2020); Zimmermann and Hauschke, Sustainability 16(11) 4723 (2024); Park et al., Journal of Industrial Ecology (2024); Tchibo and move4zero (2024); Zalando corporate (March 2024); NRF and Happy Returns, 2025 Retail Returns Landscape; California PRC 42040 to 42084 (SB 54) and 42355.51 (SB 343); CalRecycle, SB 343 Material Characterization Study (April 2025); Oregon ORS 459A.866; Maine 38 MRSA 2146; Minnesota Statutes 115A.1441; How2Recycle, Store Drop-off label guidance (2025 to 2026).