These Columbian 10" x 13" Self-Seal Mailers are made of strong and durable DuPont Tyvek material that can easily withstand the toughest conditions. The material is virtually indestructible because it isn't paper: it's puncture, tear and moisture-resistant Dupont Tyvek, making it perfect for sending and protecting your most important items. Protective envelopes provide a highly effective and useful way to send important information and items, whether from home, office or work. With exceptional durability, these self-sealing mailers can help increase the effectiveness of your important mailings and ensure that the contents and your message will be delivered intact. They feature a Release & Seal closure which requires no moisture for a secure seal and a release strip for quick, easy opening. They are also lightweight, which helps save on shipping costs. No matter what your job entails, these large mailers can help you be more efficient and effective with your correspondence and delivery of important items. White. 10" x 13" self-seal mailers. 100 per box. Tyvek is a trademark of DuPont used under license by TOPS Products LLC.