Dubl-Vue Grip-Seal Envelopes feature two windows to show the return address and addressee's information. Envelopes are compatible with most computer-generated forms, invoices and purchase orders. The Grip-Seal Closure offers a quick, no mess solution and requires no moisture. Simply peel off release strip and press down the flap for a fast, secure seal. Envelopes offer an inside security tint for added privacy of contents. Envelopes are made of premium 24 lb. bright white wove stock and have a side seam.