For a soft item that fits after folding and wrapping, compare 10x13 poly mailers such as the Metronic 10x13 100-pack , after checking width, length and thickness; a T-shirt description alone does not establish fit. Add 6x9 mailers for small accessories, 12x15.5 for sweatshirts and jeans, and 14.5x19 for hoodies and bundles. Poly film offers moisture resistance, but seams and closures are not a watertight guarantee. A padded mailer adds cushioning, not rigid crush protection; fragile or bend-sensitive items need an appropriate protective enclosure.

Buy the size that fits your packed product, not a mixed warehouse of sizes. This is desk research from the Amazon listings and supplier spec pages, checked October 31, 2026; nobody here tested these mailers.

Picks at a glance

Mailer Fits Listed details Buy
Metronic 10x13 poly mailers One folded T-shirt, leggings, a scarf 10 x 13 in, 100 pack, white, self-seal Amazon
GPI 6x9 poly mailers Small soft accessories, patches, socks 6 x 9 in, 100 pack, 2.5 mil, virgin LDPE Amazon
Metronic 12x15.5 poly mailers A sweatshirt, jeans, two light tops 12 x 15.5 in, 100 pack, white Amazon
POLYSELLS 14.5x19 poly mailers Thick hoodies, small clothing bundles 14.5 x 19 in, 100 pack, opaque white Amazon
Amazon Basics poly bubble mailer 8.5x12 Small items that need cushioning 8.25 x 11 in inside, bubble lined, 100 pack Amazon

Which size do I need?

Measure the item after folding and wrapping it with tissue or an inner bag. Uline publishes a sizing rule for flat poly mailers (listed sizes exclude the 2-inch flap):

  • Mailer width = product width + product thickness + 1.5 in
  • Mailer length = product length + product thickness + 3.5 in

A thin tee folded to 7 x 8.5 x 0.5 in needs 9 x 12.5 in by this rule, so a 10x13 fits. A thicker folded shirt at 8 x 10 x 1 in needs 10.5 x 14.5 in, which means the 12x15.5. A folded hoodie at 10 x 12 x 2 in needs about 13.5 x 17.5 in, which means the 14.5x19.

Don’t oversize either. USPS can add a nonstandard fee on Priority Mail for polybags “with contents that may shift, or cause the parcel to roll,” so assess the filled parcel’s shape and obtain the actual quote; snug packing does not guarantee a lower price.

Metronic 10x13: best first pack

The everyday Etsy size for one soft item. The listing calls it opaque, waterproof and tear-resistant with a self-seal strip. Buy one 100-pack, pack five real orders, and only then buy in bulk.

GPI 6x9: best for small soft goods

This listing is one of the few that states a thickness: 2.5 mil, made from virgin low-density polyethylene with a gray inner lining for privacy. Use it for flat, soft items only. A firm edge, zipper or buckle in a tight 6x9 bag strains the seams.

Metronic 12x15.5 and POLYSELLS 14.5x19: for bulkier apparel

Move up to 12x15.5 when a 10x13 needs squeezing to close. The 14.5x19 POLYSELLS bag is sold as hoodie-sized and suits thick knits or small Poshmark-style bundles. Large mailers are fine for coats and blankets but wrong for anything that needs to hold a shape.

When to use a padded mailer instead

Poly film resists moisture, not impact. For small items with some give, such as jewelry boxes, phone cases or cosmetics in plastic tubes, use a bubble mailer like the Amazon Basics 8.5x12. For glass, ceramics, framed art or prints, use a rigid mailer or a box; see the Etsy fragile packing guide .

Poly mailer thickness: mil, microns and GSM

Most listings say “thick” or “heavy duty” without a number. When a figure is given, it can be in mil, microns or GSM. Microns are exact (1 mil = 25.4 microns, per NIST). GSM depends on the film’s density; the estimates below use 0.92 g/cm³, the density of a typical low-density polyethylene film resin.

Film thickness Microns Approx. single-layer GSM
2 mil 50.8 47
2.5 mil 63.5 58
3 mil 76.2 70

These are illustrative film conversions, not load ratings or complete-bag weights. A bag has multiple faces, seams and a closure.

Thickness is one input: two 2.5 mil bags can differ in layer structure, seams and adhesive. Uline’s standard mailers, for comparison, are 3 mil, three-layer co-extruded polyethylene.

Labels on poly mailers

Put the label on the flattest panel, away from the seal and seams, and smooth it from the center out so it does not lift or wrinkle. Use an adhesive specified for the mailer material and its application temperature; keep the surface clean and dry. If labels keep lifting, see choosing thermal labels for adhesive types.

Who should buy which

  • First apparel order: Metronic 10x13.
  • Small, flat, soft items: GPI 6x9.
  • Sweatshirts and jeans: Metronic 12x15.5.
  • Hoodies and bundles: POLYSELLS 14.5x19.
  • Crush-sensitive items: choose adequate rigid protection from our shipping box picks .

Seal and label them with a 4x6 label printer , and weigh each bag on a shipping scale before buying postage.

Sources