Performance hydraulic roller lifters dyno developed and track tested. CNC-machined and precision ground. When used with Feuling® oil pump, they will increase critical oil flow to valves, springs, rockers, shafts and valve guides. Extend life of top end valve gear. Can also be used for OEM replacements. Made in the U.S.A. Fits 84-99 EVO, 86-90 XL. Replace OEM 18523-86B.