Our Acid-Free matboards are 4-ply and feature a White Core. With an overall size of 24" x 36", these mats fit perfectly into 24" x 36" frames. Each mat is bevel cut to enhance your 20" x 30" photos. The actual mat opening size is 19.5" x 29.5" inches so that it may safely and securely display your 20" x 30" photo, artwork, needlepoint, sign, etc. Includes backing and bags.