No. 9 invoice envelopes offer double windows for return address & mailing address. Compatible with most standard 8-1/2" x 11" computer-generated invoices & statements. Top window (1-3/16" x 3-1/2") is positioned 3/8" from left & 2" from the bottom of the envelope. Bottom window (1" x 4") is 3/8" from the left & 1/2" from the bottom. Poly windows & inside tint deliver privacy of contents. Self-sealing design makes them quick & easy to close. 24 lb. envelopes require no moisture to seal. Unique double flap design keeps the gum from sticking before use. Simply raise the lower flap & press.