Our 4-ply matboards are Acid-Free and feature a White Core. With a 20" x 20" overall size, these mats fit perfectly into 20" x 20" frames and are bevel cut to enhance your 10" x 10" photos. Actual mat opening size is 9.5" x 9.5" inches so that the mat may safely and securely house your 10" x 10" p