Made from durable polypropylene and archival safe for long-term storage. Featuring an easy-to-use zip closure to seal out the elements to help resist dust and moisture. An expanding gusset provides flexible storage for a single or a stack of art and photo materials; Ideal for carrying supplies and organizing projects too. The Art Profolio PolyZip Envelope also has a single sheet pocket in the front for a routing slip or a content sample.