This kit contains the power rotor or driving spindle, 2 idler rotors, a shaft key and balancing piston. They are sold as a set as the parts must intermesh and have very small clearances. They are sold as a set individually (G012) or included as part of a major overhaul kit with gaskets and seals in the G054 Major Kit. An overview can be seen in our IMO Spare Part coding PDF above