Our 4-ply matboards are Acid-Free and feature a White Core. With a 12" x 12" overall size, these mats fit perfectly into 12" x 12" frames and are bevel cut to enhance your 8" x 8" photos. Actual mat opening size is 7.5" x 7.5" inches so that the mat may safely and securely house your 8" x 8" photo