20x28 Matting for Picture Frame Dark Blue with Cream Core and 16x24 Opening Size (B334MAT) MAT SIZE: This matting fits a 20x28 frame. (frame not included) OPENING SIZE: This mat fits a 16x24 photo / print. (Actual opening size is 15.5x23.5) Matting Material is Crescent Mat Board. Dark Bottle Blue Finish / Cream Core with White Backing (PH Neutral). This listing includes (1) Custom Cut Mat. (The size selected represents the OUTSIDE dimensions of the matting.)