Our 4-ply matboards are Acid-Free and feature a White Core. With a 8.5" x 11" overall size, these mats fit perfectly into 8.5" x 11" frames and are bevel cut to enhance your 5" x 7" photos. Actual mat opening size is 4.5" x 6.5" inches so that the mat may safely and securely house your 5" x 7" pho