The chrome housing is made specifically for the 4 LED Courtesy Light, Add On series part 20-6811C_ . Chrome screws are provided to attach the light into the housing and the base is a thread stud mount with an anti-vibration rubber washer. This light is very versatile in its applications on the bike, trike or trailer turning the courtesy lights into driving, marker, side lights and more. Also used for Add On part 18-113 series fork light kits. Single.