No. 9 Envelopes
No. 9 Envelopes (3-7/8" x 8-7/8") available from small to large quantities.
#9 envelopes are ideal business reply envelopes. No. 9 envelopes are designed to fit nicely inside the standard No.10 Envelope.
#9 Regular Envelopes are one of the most popular commercial-sized envelopes available, 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.