Precision angular contact ball bearings have **9, *0 and *2 three diameter series, and the contact angle is *5 °(the suffix is C) and *5 ° (the suffix is AC). Bearing with big contact angle is used for the occasion which needs high axial rigidity and large axial load capacity.

High-speed, super high-speed bearing (such as: electric spindle bearing) have CETA (*5 °) and ACETA (*5 °) on suffix. These bearings have much more steel ball bearings, and have enough rigidity and carrying capacity.

Series **9 or *0 are applied in the occasion with small radial space and very high speed. And *2 series is suitable for medium and heavy load occasion. But we should choose **9series when it needs the highest rigidity. Because there are many steel ball bearings of **9 series, so they have high bearing rigidity. Due to the cross-sectional area of **9 series bearing is small, the diameter of the spindle rigidity can be increased, and the rigidity of spindle also increased, thus greatly improving the rigidity of machine. So the **9 series bearing are more widely used than the other two series in the spindle of machine tool.