21x36 Matting for Picture Frame Orange with Cream Core and 17x32 Opening Size (B152MAT) MAT SIZE: This matting fits a 21x36 frame. (frame not included) OPENING SIZE: This mat fits a 17x32 photo / print. (Actual opening size is 16.5x31.5) Matting Material is Crescent Mat Board. Tangerine Orange 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.)