Quality Park #8 5/8 Double Window Envelopes show the sender address and receiver address for billing invoices, business checks and other important statements. These security envelopes have a reflex blue pattern to protect sensitive information, even when envelopes are held up to light. These business envelopes are made of 24 lb white wove paper with side seams for a professional appearance. Seal these mailing envelopes closed by simply adding moisture to the gummed, commercial flap. Available in boxes of 500 so you never run out! Envelope dimensions are 3 5/8 x 8 5/8 inches. Top window dimensions are 7/8 x 3-/2 inches, 5/8 inches from the left and 2 /4 inches from the bottom. Bottom window dimensions are x 4 inches, 5/8 inch from the left and a 5/8 inch from the bottom.