Twin Power 37-99 Big Twin Except 99 Twin Cam Oil Pump Check Ball Replaces H-D 8866Twin Power's Oil Pump Check Ball for 1937 1999 Big Twin models (excluding 1999 Twin Cam) is a precision steel component that works with the pump check system to help maintain proper oil pressure, prevent drain back when the engine is off, and provide a reliable replacement option for worn or pitted original parts in stock or rebuilt motors. This Part Fits: Year Make Model Submodel 1971 1980 Harley Davidson FLH Electra Glide Base 1994 1998 Harley