Consisted of a pair of rings, retainer and a group of steel balls, is the common and widely used bearings for its simple structure and easy operation. It can carry great radial load and a little axial load from all directions. If you increase, to some extend, the radial tolerance of this kind of bearings, it can be used as angular contact ball bearings and carry relatively higher axial load. After being mounted on the shaft, the bearings serve a function to limit the axial displacement between shaft and bearing housing to the tolerance range. And the bearing can keep well performance even if relative tilt(degree of tilt subject to the tolerance range) appeared between shaft and housing. Once tilt exist, service life will be shortened.