Clearance of a rolling bearing is defined as the amount of possible displacement of one ring relative to the other in the radial or axial direction. It can be classified as the following five groups.

Electric motor bearings like deep groove ball bearings and cylindrical roller bearings require special clearances that indicated by CM,CT.
For those sets of single row angular contact ball bearings of back to back (X) or face to face(O) arrangement, the axial clearance can be classified into three groups.

CA ?Axial internal clearance smaller than CB
CB ?Normal axial internal clearance
CC ?Axial internal clearance greater than