Our acid-free Steel Blue matboards are 4-ply and feature a white core. With an overall size of 13x13, these mats with Square openings fit perfectly into 13x13 frames and are bevel cut to showcase your 9x9 photos. Actual mat opening size is 8.5x8.5 inches so that it may safely and securely house your 9x9 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!