Thrust ball bearings have two rings of equal size. Radial ball bearings - Radial ball bearings are designed to carry both radial and (light) axial (thrust) loads, while thrust ball bearings are ...
while other ball bearings adhere to ISO 492 or its regional equivalent (DIN, KS, etc.) There are five accepted levels of the ABEC/ISO 492 scale and the level is not related to the size of the bearing.