Our acid-free Fresh Linen Canvas matboards are 4-ply and feature a white core. With an overall size of 20x24, these mats with Oval openings fit perfectly into 20x24 frames and are bevel cut to showcase your 17x20 photos. Actual mat opening size is 16.5x19.5 inches so that it may safely and securely house your 17x20 photo, artwork, needlepoint, sign, etc. This pack includes 1 Single Matboard Show Kit With Acid Free Backing & Clear Bag. Proudly made in the USA by Country Art House!