12x33 Matting for Picture Frame Black with Cream Core and 8x29 Opening Size (B221MAT) MAT SIZE: This matting fits a 12x33 frame. (frame not included) OPENING SIZE: This mat fits a 8x29 photo / print. (Actual opening size is 7.5x28.5) Matting Material is Crescent Mat Board. Black 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.)