The polycarbonate piston head have built-in pressure bearings to reduce friction from the spring. The piston head are ventilated making sure that the rubber seals are pressed against the cylinder sides when the air is compressed. This gives optimal compression of the air and minimizes wear and tear on the rubber seal.Ultimate’s cylinder parts are designed to give the best possible air compression and durability. For this reason we recommend always using Ultimate cylinder parts and not combining or mixing with other upgrade parts as this can affect the result and performance of the upgrade