Bore: 3.448in. Compression: 9:1 Compression Sizing: 0.010in. OversizeHigh-quality premium performance pistons are a special hypereutectic T5 aluminum alloy. This alloy makes it possible to build a lightweight piston that makes more power, runs great, uses less fuel and lasts longer than other pistons. Kit includes 2 cast pistons, 1 set of Hastings moly rings and piston pin clips. Instructions included.1941-1950 fits H-D F 1941-1964 fits H-D FL 1953-1964 fits H-D FLF 1965-1969 fits H-D FLFB Electra Glide 1958-1964 fits H-D FLH Duo-Glide 1970-1979 fits H-D FLH Electra Glide 1955-1957 fits H-D FLH Hydra-Glide 1965-1969 fits H-D FLHB Electra Glide 1955-1964 fits H-D FLHF 1970-1972 fits H-D FLHF 1965-1969 fits H-D FLHFB Electra Glide 1971-1978 fits H-D FX Super Glide 1974-1978 fits H-D FXE Super Glide 1979 fits H-D FXEF Fat Bob 1977-1979 fits H-D FXS Low Rider