High Quality Self Sealing Mailers. Self Sealing Poly Courier Shipping Mailers! UPS, FedEx & USPS APPROVED Superior tear and puncture resistance. The dark inner layer provides confidentiality Pressure sensitive adhesive provides a high strength durable closure, water and dirt resistant High-efficiency mailers are perfect for shipping a wide variety of non-fragile items. Water, Tear and Puncture resistant. Lightweight saves on postage High strength seams allow for over-stuffing.