In short: For most e-commerce brands, a custom poly mailer should be a 3-layer co-extruded LDPE/HDPE film at 0.06–0.08 mm (2.5–3 mil) for apparel and soft goods, and 0.08–0.10 mm (3–4 mil) for heavier or multi-item orders, with a permanent hot-melt self-seal strip. Size the bag so the folded product fills about 70–80% of the usable area, and add a second adhesive strip only if your return rate justifies it. Heyi Custom Bags produces printed poly mailers from a 5,000 pcs per design minimum at its factories in Dongguan, China and Haiphong, Vietnam.
Poly mailers are the lightest, lowest-cost shipping pack for anything that does not need a rigid box. The choices look simple — size, thickness, seal, print — but each one changes shipping cost, damage rate and how the parcel looks on a doorstep. Here is what a brand or wholesale buyer should settle before requesting a quote on custom poly mailer bags.
Film Structure: Why 3-Layer Co-Extrusion Matters
Quality poly mailers use a 3-layer co-extruded LDPE/HDPE film. LDPE gives puncture resistance and a smooth printable surface; HDPE adds stiffness and tear strength so the bag survives conveyors and sorting arms. The usual build is white or colored outside and grey or black inside, making the mailer fully opaque. Mono-layer film is cheaper but tears more easily at the same gauge.
The same structure can be run with 30–100% PCR recycled resin, or switched to a PLA/PBAT compostable film such as our compostable poly mailer bags. Trade-offs in shelf life and cost are covered in our eco-friendly packaging bags guide.
Standard Sizes and What Fits Inside
Mailers are quoted by outside width x length, with the adhesive lip (usually 40–50 mm) stated separately. Usable length is about 20–30 mm less than the stated length once the bottom seal and flap fold are counted.
| Size (inches) | Size (mm, approx.) | Typical contents |
|---|---|---|
| 6 x 9 | 150 x 230 | Jewelry, phone cases, socks, small cosmetics |
| 7.5 x 10.5 | 190 x 270 | One T-shirt, underwear sets |
| 10 x 13 | 250 x 330 | 1–2 T-shirts, leggings, light knitwear |
| 12 x 15.5 | 305 x 395 | Hoodies, jeans, 2–3 garments |
| 14.5 x 19 | 370 x 480 | Jackets, bedding, multi-item orders |
| 19 x 24 | 480 x 610 | Bulky soft goods, pillows, bundles |
Sizing rule: lay the folded product flat, add 25 mm per side in width and 50 mm in length, then round up to the nearest standard size. Most brands standardize on three or four sizes rather than one per SKU.
Thickness: 0.05–0.10 mm (2–4 mil)
Thickness is the largest cost driver after quantity, so match it to the product instead of defaulting to the heaviest gauge. Heyi Custom Bags can extrude 0.01–0.2 mm film, but poly mailers almost always sit in the range below.
| Thickness | Mil | Recommended for |
|---|---|---|
| 0.05 mm | 2.0 | Light single garments, domestic shipping, lowest cost |
| 0.06 mm | 2.5 | Most apparel and accessory brands |
| 0.075–0.08 mm | 3.0 | Multi-item orders, international parcels, hard-edged items |
| 0.10 mm | 4.0 | Heavy goods, boxed shoes, premium unboxing feel |
Structure matters as much as gauge: a 3-layer film at 0.06 mm will beat a mono-layer film at 0.075 mm on tear tests. Dropping a 10 x 13 inch mailer from 0.08 to 0.06 mm also saves roughly 4–5 g per parcel.
Self-Seal Options
- Single permanent strip – hot-melt adhesive under a release liner; once pressed it cannot be reopened without tearing the bag. Default for one-way shipping.
- Double adhesive strip – a second strip lower on the bag lets the customer reseal it for returns. Worth it for apparel with 20–30% return rates; unnecessary for consumables.
- Tear strip – a perforation below the seal opens cleanly without scissors and leaves the bag intact for a return. Often paired with the double strip.
Specify adhesive width (typically 15–20 mm) and confirm the glue stays tacky below 0°C if you ship to Canada or northern Europe in winter.
Printing and Branding
Mailers are flexo or gravure printed before bag making, so full-coverage patterns and inside prints are both possible. Heyi Custom Bags prints up to 10 colors with Pantone matching. Most brands choose a one- or two-color logo with a return-address block, or a full-coverage design like our thank-you printed poly mailers. Leave an unprinted white panel where thermal labels will be applied so barcodes scan reliably.
Checklist Before You Request a Quote
- Sizes (width x length plus lip) and quantity per size — minimum 5,000 pcs per design.
- Thickness per size and film type: co-ex LDPE/HDPE, PCR content, or compostable.
- Outer and inner colors; seal type (single, double, tear strip).
- Print colors with Pantone references and vector artwork (AI or PDF, fonts outlined).
- Destination and incoterm, so freight and the 15–25 day production lead time can be planned.
FAQ
What thickness should a custom poly mailer be for clothing?
For single garments and most apparel orders, 0.06 mm (2.5 mil) 3-layer co-extruded LDPE/HDPE film is the standard choice. Use 0.08 mm (3 mil) for multi-item or international parcels and 0.10 mm (4 mil) for heavy or boxed goods.
What is the minimum order quantity for custom printed poly mailers?
Heyi Custom Bags produces custom printed poly mailers from a minimum of 5,000 pieces per design. We serve brands, wholesalers and distributors buying in volume, and the MOQ applies to every size and print design.
Are self-seal poly mailers tamper evident?
Yes. The permanent hot-melt strip bonds to the film so the bag cannot be opened and resealed without visible tearing. A double adhesive strip adds a second seal for returns without affecting the tamper evidence of the first.
Can poly mailers be made from recycled or compostable material?
Yes. The same 3-layer mailer can be made with 30–100% PCR recycled polyethylene, or as a PLA/PBAT compostable film with a compostable adhesive strip, keeping the standard self-seal and printing options.
Custom Poly Mailers From Heyi Custom Bags
Heyi Custom Bags has made printed packaging bags since 2016 at three factories in Dongguan, China and one in Haiphong, Vietnam, with around 500 staff and ISO 9001, ISO 14001 and GRS certification. We ship directly to the USA, UK, Canada, Australia and the EU, with a 15–25 day lead time and a 5,000 pcs per design minimum. Send your sizes, thickness and artwork through our request a quote page and we will return a specification and sample plan.