Business Source Self Seal Envelope, Reg, Plain, No. 10, 4-1/2" x 9-1/2", 500/BX, WE (BSN04644) Box of 500No. 10 invoice envelopes offer a self sealing design that 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: 04644 Brand Name: Business Source Product Name: No. 10 Self seal Invoice Envelopes Marketing Information: No. 10 invoice