Rolling bearing code are consist of basic code, fronting code and postposing code. It was expressed by alphabet and number.
1．Basic code
   Basic code shows inner diameter, outer diameter, width and type of the bearings. It consists off mostly five digits. Details explanation are as below:
   Inner bearing is expressed by H number, first digit from right side of basic code. For usual bearing with inner diameter at 20-480mm which can be divided by 5, two digits will be showed for inner diameter value. For example, 04 reflects inner diameter at 20mm, 12 reflects inner diameter at 60mm, etc. For others, 00 reflects 10mm, 01 reflects 12mm, 02reflects 15mm, 03 reflects 17mm. Other expression code will also be stipulated for inner diameter less than 10mm or more than 500mm.
    Bearing diameter(for different bearings in outer diameter and width with same structure and inner diameter) is expressed by third digit from right side of basic code. For example, for radial bearing or radial-thrust bearing, 1 reflects particular lightweight, 2 reflects lightweight, 3 reflects middleweight, 4 reflects heavyweight. Thrust bearing’s expression mode are the same with radial bearings except their 1 reflects particular lightweight.
    Bearing width (for different bearings in width with same structure and diameter)is expressed by forth digit from right side of basic code.width code 0 usually not expressed for most bearings, it only shows for self-aligning roller bearing and taper roller bearing. Diameter code and width code are both named dimension code.
    Bearing type is expressed by fifth digit from right side of basic code.(cylinder roller bearing and needle bearing are expressed by alphabet.)
Note:
 
2．Fronting code
    Fronting code expresses sub-components of bearings, it shows in alphabet. Eg, L reflects separable rings of separable bearing, K reflects rolling elements and cage of bearings.
In reality, there are two many different type of bearings with complex corresponding  expression code. The basic type of bearings are explained as above for common use of bearings.
 
3．Postposing code
    Postposing code expresses different structure, tolerance, material and some specific requirement of bearings. Here refer to some usual expression code as below:
    Inner structure code shows different inner structure of same type bearings, it located right after basic code. Eg, C, AC, B respectively reflects 15°,25°,40° angular contact ball bearings.
    There are six level of bearing tolerance, level 2, level 4, level 5, level 6, level 6X and level 0. Corresponding code are P2, P4, P5, P6, P6X, P0. Level 6X only used for taper roller bearing, level 0 used for common bearings and not be marked usually.

    There are 6 groups of radial clearance, group 1, group 2, group 0, group 3, group 4 and group 5. Radial clearance increases successively. Group 0 used for common clearance and not be marked usually. Other groups are expressed by C1, C2, C3, C4, C5 in code.