8"x10" outside size. 4.5"x6.5" opening size for 5x7 inch photo. 4-ply thickness. White core and acid free Made in the USA 8x10 matting. Opening is cut to 4.5"x6.5" to securely hold a 5"x7" photograph or art print in an 8x10 inch frame (frame not included). The matboard has a bright white core. Cut with a 45 degree bevel. 4 ply/.055" thick. Acid free and PH neutral. Colors are matched as close as possible but can vary depending on each person's screen settings. Matting gives your framed photos a professional look and also protects them from damage by keeping it from making contact with the glass where moisture would get trapped and warp/discolor your photo.