Question: what size are 6x9 envelopes?
Answer: A9 - (5 3/4 x 8 3/4) - Used as an outer envelope. Fits cards, invitations, or inserts up to 5 1/2 x 8 1/2. A10 - (6 x 9 1/2) - Also known as a 6x9 envelope. Fits envelopes, invitations, or inserts up 5 7/8 x 9 3/8.