A rolling element bearing is a type of bearing used to ensure smooth and efficient operation in machines with rotary motion such as car automobile wheels, engines, turbines, medical equipment, and more. A ball bearing is a type of rolling element bearing that, while facilitating motion, serves three main functions: carrying loads, reducing friction, and positioning moving machine parts. Ball bearings use balls to separate races, reducing surface contact and friction across moving planes. The rotation of the balls creates far less friction than two flat surfaces rubbing against each other. However, because there is less surface contact, ball bearings typically have a lower load capacity than other rolling element bearings of similar sizes.