According to the ISO classification standards, precision bearings are divided into: P0, P6, P5, P4, P2. The grades are increased in turn, where P0 is ordinary precision, and the other grades are precision grades. Of course, different classification standards, different types of bearings, their classification methods are different, but the meaning is the same. The performance of precision bearings requires the rotating body to have high runout accuracy, high-speed rotation, and small friction and friction changes.