This venturi exhaust fan frame is has a green powder coat and is made of steel. It is suitable for 20-inch blades and measures 24 1/8 width x 24 1/8 height x 10 1/2 inches deep. The opening required is 20 3/4 inches and the venturi depth is 3 3/4 inches. Dimension A is 24 1/8 inches, dimension B is 3 3/4 inches, and dimension C is 10 1/2 inches.