For use with two or more batteries. For single or dual engine systems. Permits selection between batteries for starting and charging or operation of both batteries in parallel. Allows the addition of an extra battery for use with accessories. "OFF" position also acts as an emergency disconnect in the event of an electrical problem. Rated at 250 amps continuous, 360 amps momentary. Size: 5-1/4"Dia., 2-5/8"depth. Red plastic housing with black plastic knob.