Our acid-free Grey 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 11x17 photos. Actual mat opening size is 10.5x16.5 inches so that it may safely and securely house your 11x17 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!