Allows interruption of the main battery cable for effective protection against unauthorized use of the boat. Positive or negative cable can be switched off as required. Key can be removed in "off" position, current interrupted. Seawater-proof. Tin-plated contacts. U.L. listed. Line connection: 2 screw terminals, M10. Maximum load 12V: 1000 A (10 sec.) 24V: 500 A (10 sec.). Black base, red knob. Size 2-1/4" dia. Type Battery Master