This item comes with 50 pre-cut mats, 50 backing boards and 50 clear bags. The opening size is 3.5"x5.5" for 4x6 print. The mats are beveled cut. The backing is also 4-ply. The re-sealable adhesive strip of the clear bag is below the opening of the bag instead of on the flap. Our acid-free cream core matboards are a 4-ply paper mat that provide the aesthetic and design benefits of a bright white bevel. It can be used for matting photos, art, and needlepoint. Also great for crafts, backboards, signs, children s projects, and school projects.