Deep groove ball bearings, which are widely used, are the most representative structure of rolling bearings. This type of bearing can carry not only radial load but also axial load from two directions. Featured with small friction torque, deep groove ball bearings are quite suitable for the circumstances of high speed, low noise and slight vibration. Deep groove ball bearings are widely used in the fields of automobiles, electrics, instruments, construction machineries, agricultural machineries, and many kinds of special machineries. These bearings, with various specifications, are usually divided into open type and sealed type. NNN mainly produces the open type,medium-large and extra-large size.