Business Source Self-seal #10 Envelopes - Multipurpose - #10 - 24 lb - Self-sealing - 500 / Box - White (BSN03141) Box of 500No. 10 Invoice Envelopes offer double windows for return address and mailing address. They are compatible with most standard 8 1 2" x 11" computer generated invoices and statements. Poly windows and inside tint deliver privacy of contents. Self sealing design makes them 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