10" x 13" x 1-1/2" First Class Border Expansion Mailers are made with 14 lb. DuPont Tyvek and feature a Redi-Strip closure. Protective material is strong and durable enough to easily withstand the most grueling conditions and resists punctures, tears and moisture. Everyday mailers provide a highly effective and useful way to send important information and items whether from home or work. First-class border can help increase the effectiveness of your important mailings and the assurance that your contents will be delivered. Mailers expand up to 1-1/2" to accommodate bulky items. Redi-Strip closure requires no moisture for a secure seal. Lightweight construction could help you save on shipping costs.