1000 (One Hundred S3 (Dimension 10" X 13") Poly Mailers) Tear-proof, Water-resistant and Postage-saving Lightweight Self-seal Poly Mailers Shipping bags UPS, FEDEX, USPS, NEWGISTICS, DHL APPROVED Tough and tear-proof poly mailers. Water and tamper resistant poly mailers. High strength seams allow over-stuffing. Postage-saving lightweight poly mailers.