The opening size is 11.5"x17.5" for 12x18 print + FOAM BOARD
Elmer's Foam board is 1/8" thick.
Our acid-free whitecore matboards are a 4-ply papermat that provide
the aesthetic and design benefits of a bright white bevel., Each sheet
of mat board has a richly colored front surface, a white core and a
white backing. It can be used for matting photos, art, and needlepoint.
Also great for crafts, backboards, signs, children's projects, and
Quantity 1 = 10 mats and 10 foam boards