Our Acid-Free matboards are 4-ply and feature a White Core. With an overall size of 6" x 7.5", these mats with oval openings fit perfectly into 6" x 7.5" frames and are bevel cut to enhance your 3" x 5" photos. Actual mat opening size is 2.5" x 4.5" inches so that it may safely and securely house your 3" x 5" photo, artwork, needlepoint, sign, etc.