Replaces OEM 8990/A style ball bearing. This bearing will fit will fit all models as front & rear outer cam bearings. Note: The MoCo has redesigned the Twin Cam rear outer cam bearing from ball to a roller bearing style in 2001. This was done to help prevent failing ball bearings on; specifically; rear (=driveside) cams that are heavier loaded. This 01-up roller style bearing is a 3-piece design that is more heavy duty than the roller bearing. No other parts changed during the bearing changes. The early 99-00 style ball bearings will still fit all 99-06 models front & rear. Using front & rear ball bearings present no issues on cam driven gears.