Jims Hydraulic Tappets 24621 Standard solid Big Axle rollers are designed around three working parts The outer wheel/roller has a 27% greater wall sizeless harmonic distortion for better tracking of cam lobe Pin bearings are decreased in size by 12%, which increases rpm for more precise tracking Axle size is increased 36% and doubles as the inner race, so the pin bearing and complete roller assembly now rotates around the axle instead of an inner race, eliminating all possible movement in and around the axle Sold each