Bearings

Similar to the wheel, bearings are literally components that allow other equipment to roll and serve to reduce friction between their surfaces.

They are basically composed of rings (outer ring with inner race and inner ring with outer race) and rolling elements, which can be spheres, tapered rollers, cylindrical rollers, spheres, etc. These are the rolling components that fill the space between the inner tracks and external.

These rolling components may or may not have a guide cage, used to fix and maintain the position of the rolling elements.