10″ x 13″, Open End Catalog Envelope, No Window, Western Sulphite, White Sulphite Paper, SFI Certified, Vellum Finish, Center Seam, Flap Down, Kwik-Tak, 500 Qty / Box, 500 Qty / Ctn, 27 lbs. Open End Catalog Envelopes, 10″ x 13″, 28#, White, Center Seam, Pressure Sensitive Seal (Box of 500).