Ball piston pump is a very simple pump design. It has a rotor, which revolves around an internal stator. The rotor has twelve cylinders machined out of it, and each cylinder has a ball inside, which can slide in and out of the cylinder. The balls ride along a two-railed track machined into the outer housing. The balls revolve around the pump in a perfect circle. The center point of the circle, which the balls revolve around, is offset from the center point of the stator and the rotor, the balls and the rotor have relative motion to each other. This relative motion increases and decreases the volume of each cylinder, allowing the mechanism to draw in fluid during one half cycles and expel it during the other half cycle.