Quality Park Cirrus Dupont Tyvek White Anti-Microbial Envelope 9"x12" Box Of 100, material is strong and moisture resistant Security tinted inside for privacy of contents. Redi-Strip closure requires no moisture to seal. Features a removable strip that provides a clean, quick seal immediately upon contact. Peel-off strip protects adhesive from dust for longer shelf life. Envelopes are made with a material that inhibits the growth of mold and mildew to protect the product.