Marine Emergency Kill Switch attaches to your life vest while operating a boat or personal water craft. Designed to instantly cut battery power when detached. The Magneto (Red Cap) version functions in applications where the circuit is normally open (Not Complete) with the lanyard clip in place on switch. When lanyard is pulled and clip is removed from switch, circuit is closed (complete), allowing grounding to a suitable ground such as a grounding block, the battery, or on the engine itself. The Ignition (Gray Cap) version functions in applications where the circuit is normally closed (Complete) with the lanyard clip in place on switch. When lanyard is pulled and clip is removed from switch, the circuit is open (Not Complete), resulting in interruption of current to the Ignition shutting off engine. Both kill switches include a coiled lanyard that is approximately 15" when coiled and 48" when stretched, which should be replaced if worn, cut, or frayed. Mounting hole is 5/8" in diameter. Maximum panel thickness: 5/8". Maximum 5A draw. Constructed of weatherproof injection molded nylon and Delrin with brass terminals. WARNING: Switch should be tested for proper function before each use. 420487 shown in picture. (Ignition Style).