Our acid-free White Linen Canvas matboards are 4-ply and feature a white core. With an overall size of 20x30, these mats with Oval openings fit perfectly into 20x30 frames and are bevel cut to showcase your 18x26 photos. Actual mat opening size is 17.5x25.5 inches so that it may safely and securely house your 18x26 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard. Proudly made in the USA by Country Art House!