Practical Function: This top post battery master switch is used to isolate and protect the battery's electrical system, eliminating any electrical drain on the battery when the vehicle is not in use, safely disconnecting the battery, which protects the car's computer system, alarm, car locks, and other components when the car is switched off. Simple Installation: The product is easy to use, the first step to find the car battery negative head diameter of 0.63''-0.67'' (16 ~ 17mm) negative pole column, remove the surface oxidation layer, the second step, the battery switch set in the negative pole column, and tighten the screws, the third step, the switch firmly clamped on the electrode column, the fourth step, the top green twist screw 4 ~ 5 turns of the whole car power outage, tighten the whole car immediately energized. What You Will Get: You will receive 1 x Battery Disconnect Switch, the threads on the knob are carefully crafted for ease of use, clear on/off position, loosen/twist the knob to cut off the power supply, superior performance to minimize voltage distortion, this battery disconnect switch is rust and corrosion resistant to extend the life of your vehicle's battery. High Quality Material: The brass green battery switch is made of heavy-duty, rugged zinc alloy with copper plating to resist oxidation, rust and corrosion, prevent voltage distortion, and withstand up to 400A at 12V, designed for high-current applications, and insulated ABS plastic knobs, which are ruggedly constructed to protect the wiring from dust, corrosion, and rain, for safety and durability. Wide Application: The Battery Disconnect Switch allows you to quickly and easily disconnect automotive batteries for safety, maintenance or storage. Suitable for automotive, marine, tractor, camper, boat, RV, truck batteries that have a standard 0.63''-0.67'' (16-17 mm) tapered top post terminal, and can also be used for electrical equipment. Primarily used to solve leakage and loss of charge problems caused by infrequently used cells in car, motorcycle and automotive batteries.