Tamper Evident Catalog Mailers are made with 14 lb. DuPont Tyvek that is strong enough to withstand the grueling conditions and resists punctures, tears and moisture yet is lightweight to save on shipping costs. Unique, tamper-indicating panel displays the word "opened" in read if the seal is broken. 9" x 12" envelopes feature an easy, Flap-Stik closure that requires no moisture for a secure seal. Release strip allows you to quickly and easily open. When sending critical documents, these catalog envelopes are a safe, cost-effective way to make sure your items arrive intact.