US Art Supply 8x10 Black Picture Mat Matte Sets. Includes a Pack of 100 White Core Bevel Cut Mattes for 5x7 Photos, Pack of 100 White Core Backers & 100 Clear Sleeve Bags Set of 100 pieces of 8x10 Picture Mattes for 5x7 Photos with 100 backing boards and 100 crystal clear sleeve folding flap bags. US Art Supply Brand Premium High Quality Mattes, Backers & Plastic Sleeve's The opening size is 4.5"x6.5" for 5x7 photo prints. Color: Black 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. The set is professionally Packed and Boxed to Assure that All Precautions have been made for a Save Arrival of your purchase.