Staples Tyvek flat envelope in white color measures 7 1/2" x 10 1/2" and is made of olefin material for durability. Envelope has self-seal closure for security and is sold as 100 per case..Feature self-seal closure.Constructed from 14 lb. olefin.Ten times stronger than paper envelopes.Staples Tyvek QuickStrip Flat Catalog Envelope provides superior puncture, tear and moisture protection.