No. 9 envelopes are compatible with standard, letter-size, computer-generated invoices and statements. Two poly windows allow return and mailing addresses to be displayed from contents. The 1-3/16" x 3-1/2" top window is positioned 3/8" from the left and 2" from the bottom. The 1" x 4" bottom window is positioned 3/8" from the left and 1/2" from the bottom. White wove, 24 lb. envelopes also have an inside security tint for privacy and a gum closure to seal the envelope securely.