A ball bearings is a rolling-element bearing that relies on balls to keep the bearing races apart. A ball bearing's job is to decrease rotational friction while also supporting radial and axial stresses. Ball bearings have been around for hundreds of years and have been utilized in various applications — intended to accommodate thrust and radial stresses in everything from hard drives to skateboards. On the other hand, ball bearings are also often used in situations with lower pressures.