Part of the Survivor family of virtually indestructible mailers, these security tinted catalog envelopes are made with a material that inhibits the growth of mold and mildew to protect the product. They are also made of 14 lb. DuPont Tyvek with Flap-Stik closure. Survivor mailers are made with a protective material that is strong and durable to easily withstand the most grueling conditions. The material is virtually indestructible because it is Tyvek, not paper. That means these envelopes resist punctures, tears and moisture - exactly what you want in your envelope when you're sending something important. Tyvek mailers can help increase the effectiveness of your important mailings and the assurance that the contents and your message will be delivered. Flap-Stik closure requires no moisture for a secure seal and a release strip for quick, easy opening. They are also lightweight, which could save on shipping costs.