Quality Park Survivor 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 resistantvirtually indestructible. Yet, it is still lightweight which can provide a savings on shipping costs. These 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. Seam Type: Center; Flap Type: Square; Trade Size: #15; Security Tinted: No.