Business Source Self-Seal Envelopes, Std Wind., No. 10, 4-1/2"x9-1/2", 500/BX, White (BSN42207) Box of 500No. 10 invoice envelopes offer a standard address window. Poly windows and inside tint provide privacy for your contents. Self sealing design makes envelopes quick and 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 and press. General Information Manufacturer: Business Source Manufacturer Part Number: 42207 Brand Name: Business Source Product