Paper Accents Letter Envelopes are perfect for greeting cards, invitations, letters, and more. Let someone know that they have received something special before its even opened. These envelopes are acid-free, lignin-free, buffered and archival quality. For use with 8 1/2 x 11 inch stationery. Commercial Flap. #10 size. 4 1/4 x 9 1/2 inch. #128 White. 25 pc.