This is a professional quality power supply set. The supply box can be used for dual machines with both machines attached at the same time. Allows tattoo artists to connect both liner and shader machines at the same time (requires 2 clip cords.) Just flip the machine switch on the lower left hand corner to switch power from liner to shader. The digital ultra bright LED screen makes this power supply much easier to read as well as giving it a much more accurate readout. Includes a 13 dial potentiometer with 120/220v conversion switch in back. Durable metal chassis frame, not like other fragile plastic models.