A wheel bearing is a simple device made up of two main components, the bearing itself and the race. The bearing itself consists of a metal housing that is pressed over a row of ball bearings that circle the metal housing. These ball bearings in turn ride on the race, which is a very smooth metal surface. When a wheel is rolling, the action of the ball bearings rolling against the surface of the hub that allows the wheel to spin smoothly.

Double row ball wheel hub bearings belong to the first generation auto hub bearings , composed of an outer ring, two inner rings, two sets of balls , two nylon cages and high-performance seals . at present, this kind of bearings are still used widely in all kinds of vehicles.