Kelsey type master cylinder used on all FX 4 speed models late 1979-1983 (except FXWG and FXSB) and Sportster XLS 1980-1981. This 3/4 inch bore die cast rear master cylinder is an excellent copy of the Kelsey Hayes type master cylinder. Works with forward control kit # D4888. OEM 42453-80A and 42454-80A.