Greaseless ball bearings: A revolutionary spin on a design that's been around for ages

The basic design in simple: in order to reduce rotating friction between two pieces, the bearing has an inner and an outer race. A number of balls roll in between these two races, allowing the smallest possible contact points between the inner and outer races. The balls roll a lot easier than the two pieces would slide against each other.

The ball bearing can only work if the balls are kept separated and evenly spaced throughout the races. Touching each other would produce friction, and uneven spacing would cause the bearing to be weak under loads from a certain direction. So most bearings use cages to separate and evenly space the balls.

These cages cause friction and to reduce this friction, you generally need to lubricate your bearings, often with thick grease to ensure a long lifespan.