These self-seal 15" x 20" + 4" Bottom Gusset Poly mailers are the perfect packaging material to protect your bulky apparel, bags, textbooks, or blankets from dirt and moisture during shipping and handling. Expansion poly mailers feature 4" gusseted depth which makes packing and shipping bulky items such as binders, books, jackets, and catalogs possible and convenient. Our expansion poly mailing envelopes have a peel-and-seal lip that provides a secure, tamper-evident closure and are the ultimate lightweight, low-cost shipping solution for bulky, non-fragile items.