Mat Board Center, Acid-Free Pre-Cut 16x20 White Picture Mat Set. Includes a Pack of 10 White Core Bevel Cut Mattes for 11x14 Photos, Backers & Clear Bags Set of 10 pieces of 16x20 Picture Mattes for 11X14 Photos with 10 backing boards and 10 crystal clear bags. Premium High Quality Mattes, Backers & Plastic Sleeve's. The opening size is 10.5 x 13.5" for 11x14 photo prints. Color: White The mats are beveled cut with white core and 4-ply thick (about 1.4 mm or 1/16 inch), The backing is white on both sides.