#9 Regular Envelopes (3-7/8 x 8-7/8) are one of the most popular commercial-sized envelopes available, commonly used as a reply envelope for invoice and business mailings, sent to recipients inside #10 Envelopes in order to mail something back to the sender. Constructed from 70lb. Natural Linen, this #9 size envelope is a creamy white color with a LuxTexture. Available both plain or custom printed for branding, address printing services are also available. These envelopes are sealed by a moistenable glue on the back flap.