These Quality Park Survivor 10 x 13 Inch Catalog Envelopes have sides that expand 2 inches to hold more. Made of strong 14 lb DuPont Tyvek material with a self sealing closure. Our Survivor mailers are strong enough to withstand grueling conditions. The 14 lb. material is puncture, tear and moisture resistant. These envelope mailers provide a highly effective way to send product or critical information through the mail with total confidence. Lightweight plastic envelopes also provide a savings on shipping costs over heavier paper or cardboard envelope mailers. These 10" x 13" white mailing envelopes feature easy Redi-Strip peel and seal closures that require no moisture for a secure seal, and a release strip for quick and easy access for the recipient. Whether you're sending critical business documents or re-selling items on an online marketplace, Survivor Catalog Mailers are an efficient, cost effective way to make sure your items get there intact. 100 per box. Tyvek is a trademark of DuPont used under license by TOPS Products LLC.