Our acid-free Oyster Shell White matboards are 4-ply and feature a white core. With an overall size of 16x20, these mats with Oval openings fit perfectly into 16x20 frames and are bevel cut to showcase your 13x18 photos. Actual mat opening size is 12.5x17.5 inches so that it may safely and securely house your 13x18 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!