PackageZoom (We) stock many sizes of heavy-duty mailing bags, all of which comply with UPS, FEDEX, USPS guidelines so that you can accurately calculate your mailing costs. Double Layer heavy duty mailing bags are manufactured from much tougher and durable polythene than standard mailing bags this makes them more tear-resistant. Peel and seal closure shipping envelopes: Self-seal adhesive strip secures bags instantly. Double the thickness of regular polythene mailing bags, tear and puncture resistant. Lightweight – Great alternative to postal boxes. Poly Mailers made from co-extruded material, using several layers of film for tear-resistance. White foil: Durable and lightweight foil. Very resistant against rain, dust and punctures. Solid white color. Shipping envelopes quality is outstanding: Pressure sensitive adhesive provides a high strength durable closure, water and dirt resistant. High-efficiency mailers are perfect for a wide variety of non-fragile items.