Reed style breather to fit S&S oil pump as used in all S&S T-Series (Twin Cam style) engines and OEM pump in 03-10 OEM engines. Will tackle problems with OEM engines as Oil Carry Over (blowing oil out of the breather system); a common problem for years. Usually at sustained high speeds and worse with big inch engines. This problem can still be present in OEM Twin Cam engines. S&S designed this aluminum crankcase breather valve containing four steel reed valves; which effectively prevents wild turbulence in the cam chest and rocker boxes. Air and oil mist can escape from the crankcase; but is not allowed to re-enter. Any oil blowing out of the crankcase breather is stopped. A slight increase in horsepower (one to two HP) and torque can be expected. The breather valve is installed over the pinion shaft; inside the pinion bearing bore; and retained between the bearing outer retaining ring and the oil pump. Note: Will not fit TCB (Softail) models. Replacement parts: 970628Seal. 970629O-ring (for 99-02 FLT; Dyna). 970630O-ring (for 03-06 FLT; 03-05 Dyna). 970631Reed valve. 970632Reed valve stop. 970634Reed valve screws. 970610Wave spring (for 99-06 FLT; 99-05 Dyna with S&S pump). 970635Wave spring (for OEM & S&S cases with stock oil pump). 970636Wave spring (for S&S .375" wider SA cases with stock oil pump). 970637Wave spring adapter (for S&S .375" wider ''Special Application'' cases with S&S oil pump).