Weatherhood, For Blade Diameter 18 in, For Cut-Out Height 20 1/2 in, For Cut-Out Width 20 1/2 in, For Cut-Out Height (With Wall Collar) 23 5/8 in, For Cut-Out Width (With Wall Collar) 23 5/8 in, Overall Height 22 1/4 in, Overall Width 22 1/4 in, Overall Depth 18 1/4 in, Material Steel, Thickness 20 ga, Finish Galvanized