|Part numbers 15005D (Model 16 planetary gear) and 151130 (Model 16 planetary bearing) are no longer available. These parts have been replaced by part numbers 15006NR (New Model 16 planetary gear) and 151150 (New Model 16 planetary bearing). The "new" style gears and bearings have been used for the past six years in all revision 4 series Model 16, Model 16D, Model 20D, Model 50D and Model 52T reducers. The "new" gears and bearings will work in revision 3 reducers, but they must be purchased and installed in sets (one 15006NR and two 151150), since the old bearings are not compatible with the "new" gears and the "new" bearings are not compatible with the old gears. It is very difficult to discern between the old and "new" style visually because there is only a 1mm differentiation.