Security Window Envelopes require no moisture to seal. Raise the lower flap and press. The unique double-flap design keeps gum from sticking until the envelope is ready to mail. Inside tint is designed for enhanced privacy. Window (1-1/8 x 4-1/2 ) is positioned 7/8 from left and 1/2 from bottom. Self-sealing No. 10 envelopes are made of a white wove material. 24 lb.