Business Source BSN04645 Self Seal Envelopes- Tint-Regular- 4.5 in. x 9.5 in.- 5 No. 10 invoice envelopes offer an inside security tint to 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.