These 10x13 Designer Print Flat poly mailers are postal approved shipping mailers; they are packaged in packs of 100. They are non-transparent so your contents are not visible water resistant due to the self-sealing adhesive strip. A Superior product that provides lightweight shipping but it s durable and tear resistant the added silver lining inside provides protection from shipping abrasions. Make a definite impression with Designer Print Flat Poly Mailers. They are approved shipping mailers with all carriers.