Permits current to be carried by either of 2 batteries, by 2 batteries simultaneously or cuts off all current at source. Ignition protected and conforms to USCG safety standard for ignition protection. Durable, fracture resistant with high temperature engineered plastic case, knob and insulator. Vaporproof, waterproof, dust proof and corrosion resistant. UL approved. Can be operated through ON positions with engines running. Engines must be shut down before moving to OFF position. Functions with alternators or generators. Has three 3/8" diameter heavy copper stud terminals with brass hex nuts. Made in the USA. Includes wiring instructions. May be surface mounted or installed through panel with 3-5/16" diameter clearance hole. Flange is 6" with a height of 2-5/8". Four positions: OFF, ON-#1 Battery, ON-both batteries, and ON-#2 battery. Electrical rating is 310 amps continuous, 500 amps intermittent and 6-36V DC.