Golden State Art, Pack of 50, Acid-Free White Pre-Cut 5x7 Picture Mat for 4x6 Photo with White Core Bevel Cut Frame Mattes Set of 50 white 5x7 WhiteCore Picture Frame Mats High Quality Mats Opening size is 3.5" x 5.5" inches for 4x6 Pictures Mats are beveled cut and are 4-ply thick (1.4 mm or 1/16 inch) All acid free, perfect from hobbies to art gallery exhibits.