No. 10 business envelopes feature DuPont Lightweight Tyvek for strong, moisture-resistant mailing. Security of contents is enhanced by an inside printed tint pattern. Each envelope is treated with an antimicrobial agent to protect the envelope against the growth of bacteria, mold, mildew, fungus and odors. Convenient Red-Strip closure requires no moisture seal. Simply peel off the removable strip, and the adhesive underneath provides a clean, quick seal immediately upon contact. The peel-off strip protects adhesive from dust for longer shelf life.