INDESTRUCTIBLE DUPONT DESIGN Lightweight Yet Strong, Durable Tyvek Material Resists Ripping, Tearing, Punctures, Rain, Moisture & Other Common Postal Threats SUPERIOR SHIPPING PROTECTION Double Reinforced Construction, Opaque Color & Super Sticky Adhesive Offers Maximum Security for Confidential Business Mail CONVENIENT SELF SEAL CLOSURE Peel Back the Sticker to Quickly & Effortlessly Seal & Send; Open End Catalog Orientation Enables Fast Paper & Packet Stuffing HEAVY DUTY ENVELOPES They are Practically Indestructible and provide superior protection from tears, punctures and moisture; Also, they are self-sealing and secure