Ball bearings are perhaps the most common type of bearing and used in a very wide range of applications. The two main components of a ball bearing are the inner race (which holds the balls) and the outer race (which supports the balls). Typically, the balls themselves are made from steel, or some other hard material, and they run between the inner and outer races. With no other wording, the concept of ball bearings would be much less, if at all, clear.