The precision of bearings is mainly divided into dimensional precision and rotational precision. The precision level has been standardized. According to the ISO classification standard, precision bearings can be divided into five levels: P0, P6, P5, P4, and P2. The current code generally adopts the German DIN standard. P0 (0 level), P6 (6 level), P5 (5 level), P4 (4 level), and P2 (2 level). The precision level increases in sequence, among which P0 is the ordinary precision of bearing products, and other levels belong to the precision level. The higher the level, the higher the running precision, high-speed rotation, and friction and friction change requirements of the bearing. P0 represents the lowest precision level in bearings, and P2 represents the highest precision level in bearings. Bearings of various precisions are distinguished not only in processing technology, but also in value.