This shim is installed between the differential carrier bearing outer race and the sideplate to adjust backlash on Webster Mk9 / Model 400 and Formula Mazda gearboxes. The 2.89" OD fits behind the LM501310 bearing cup used in Webster sideplates. Sold individually.
Note: Does not fit Hewland sideplates. Hewland sideplates use a larger (3" OD) bearing and require a larger spacer.