Our acid-free Oyster Shell White matboards are 4-ply and feature a white core. With an overall size of 24x36, these mats with Oval openings fit perfectly into 24x36 frames and are bevel cut to showcase your 20x24 photos. Actual mat opening size is 19.5x23.5 inches so that it may safely and securely house your 20x24 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!