This adapter is used to cover the threads on the inlet of a 900 series Amal Concentric carburetor, so that a non-threaded air cleaner can be fitted. This threaded adapter provides a seal when used with the rubber Airbox connector on 1971 and later Triumph and BSA twin-carburetor models. We recommend using a light application of anti-seize compound on the threads when screwing onto the inlet of the carburetor to ensure a tight connection. These adapter rings are sold individually.