Envelopes come in many sizes for different occasions. A-Styles are for Announcement and are the square-shaped envelopes that typically carry invitations. The A-Styles available are A2, A6, A7, A8, A10
Commercial or also known as Regular Envelopes, are the wide envelopes used for letter-size mailing such as bills. The Commercial Envelopes available are #6½, #6¾, #7¾, #9, #10 and may have a window on the front left or right.
Also available Remittance Envelopes #6¾, #9 with tear-off flap