Our acid-free White matboards are 4-ply and feature a white core. With an overall size of 16x16, these mats with Square openings fit perfectly into 16x16 frames and are bevel cut to showcase your 5x5 photos. Actual mat opening size is 4.5x4.5 inches so that it may safely and securely house your 5x5 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!