Our acid-free Metallic Gold matboards are 4-ply and feature a white core. With an overall size of 18x24, these mats with Oval openings fit perfectly into 18x24 frames and are bevel cut to showcase your 15x21 photos. Actual mat opening size is 14.5x20.5 inches so that it may safely and securely house your 15x21 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!