We offer a large selection of Dura-Bag Flat Mailers. You can search many types of Dura Bag Flat Reinforced Mailers, Dura Bag Self Sealing Flat Reinforced Mailers and Dura Bag Expandable Reinforced Mailers. Dura Bag Flat Reinforced Mailer is fiberglass strands laminated to kraft paper create tough mailers that resist tears and punctures. Lightweight to reduce shipping cost. Dura Bag Expandable Reinforced Mailer is fiberglass strands laminated to kraft paper create tough mailers that resist tears and punctures. Lightweight to reduce shipping cost. Tape, staple, or stitch to close.