US Art Supply Art Mats Acid-Free Pre-Cut 5x7 Black Picture Mat Matte Sets. Includes a Pack of 50 White Core Bevel Cut Mattes for 4x6 Photos, Pack of 50 Backers & 50 Clear Sleeve Bags Set of 50 pieces of 5x7 Picture Mattes for 4x6 Photos with 50 backing boards and 50 crystal clear sleeve folding flap bags. Art Mats&trade; Brand Premium High Quality Acid-Free Mattes, Backers & Plastic Sleeve's The opening size is 3.5"x5.5" for 4x6 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. The opening size is 3.5&#034;x5.5&#034; for 4x6 photo prints The mats are beveled cut with white core and 4-ply thick (about 1.4 mm or 1/16 inch), The backing is black on both sides Mat board is suitable for general purpose framing and is acid-free 50<span class="a-text-bold"> - 5x7</span> Black Picture Matte Frames for 4x6 Photos 50 - Backing boards 50 - Crystal clear sleeve folding flap bags