Roof Curb, For Fan Base Size 34 in to 39 1/2 in, Curb Height 12 in, Curb Inside Width 28 1/2 in to 37 in, Curb Outside Width 32 1/2 in to 41 in, Material Steel, Standards UL 705, For Use With 34 in to 39 1/2 in Square Base, Adjustability Adjustable,...