Looking for a #10 security single window envelope, this single window security tint envelope is the perfect choice. It keeps confidential information from showing and has a gummed flap that seals securly when moistened. Envelope size is 9 1/2 x 4 1/8 Window size 4 1/2 x 1 1/8 Window placement 7/8 from left - 2 1/2 from top.