Rolling bearings are divided into radial bearings and thrust bearings according to the load direction or nominal contact angle they can bear. The radial contact bearing is a radial bearing with a nominal contact angle of 0, and the radial contact bearing is a radial bearing with a nominal contact angle greater than 0 to 45. The axial contact bearing is a thrust bearing with a nominal contact angle of 90, and the thrust angular contact bearing is a thrust bearing with a nominal contact angle greater than 45 but less than 90.