The RVK1A Broan Roof Ducting Kit is for roof ducting installation of exhaust fans with a 3 in. or 4 in. duct. The black steel roof cap features a built-in back draft damper and bird screen. Included is 8 ft. of 4 in. diameter flexible foil ducting that conforms to UL 181 Class 1 Air Connector requirements. For a 4 in. round duct, the kit ...