Our acid-free White matboards are 4-ply and feature a white core. With an overall size of 15x15, these mats with Square openings fit perfectly into 15x15 frames and are bevel cut to showcase your 11x11 photos. Actual mat opening size is 10.5x10.5 inches so that it may safely and securely house your 11x11 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!