Quality Park® Survivor® Expanding Catalog Mailers are made with durable 14 lb DuPont™ Tyvek®, which is strong enough to withstand the most grueling conditions. The material is puncture, tear and moisture resistant—virtually indestructible. Yet, it is still lightweight which can provide a savings on shipping costs. Envelopes expand up to 2" for bulkier items, like books, large contracts and more. These 10" x 13" white mailing envelopes feature an easy Flap-Stik® closure which requires no moisture for a secure seal and a release strip for quick, easy opening. Whether your sending critical 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. 25 per box. Tyvek® is a trademark of DuPont used under license by LSC Communications US, LLC d/b/a TOPS Products.