OEM Quality Park Redi-Seal Security Window Envelopes come in a box of 500. These self-sealing No. 10 envelopes require no moisture to seal; simply raise the lower flap and press. The unique double-flap design prevents gum from sticking until the envelope is ready to mail, and the inside tint enhances privacy. The window measures 1-1/8" x 4-1/2" and is positioned 7/8" from the left and 1/2" from the bottom, ensuring your address is clearly visible.