Poly String and Button Booklet Envelope is made of tough, brightly colored polypropylene for long lasting durability. Features gusset that expands up to 1-1/4in. to accommodate bulkier materials. Envelope's heavy-duty string and button closure is designed for everyday use. Smead 89521 Clear Poly Envelopes with String-Tie Closure - Letter - 8 1/2in. x 11in. Sheet Size - 1 1/4in. Expansion - Polypropylene - Clear - 5 / Pack is one of many Open End & Catalog Envelopes available through Office Depot. Made by Smead.