Gladstone 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. Gladstone envelopes measure 3-9/16" x 5-9/16" in size and are made with 24# white sulphite paper. Gladstone, Baronial 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.