#5 envelopes are a particular style of announcement envelope with a large, pointed seal flap and diagonal seams most commonly used for greeting cards or social stationary. #5 Baronial envelopes measure 4-1/8" x 5-5/8" in size and are made with white sulphite paper. #5 envelopes are perfect for that formal look when sending invitations or R.S.V.P. cards. The Supplies Shops also offers the panel cards that would fit these envelopes.