Tapered roller bearings consist of four interdependent components: the cone (inner ring), the cup (outer ring), the tapered rollers (rolling elements) and the cage (roller retainer). Metric series medium- and steep-angle tapered roller bearings use contact angle code “C” or “D” respectively after the bore number, while no code is used with normal-angle bearings. Medium-angle tapered roller bearings are primarily used for the pinion shafts of differential gears in automobiles.