Battery isolation solenoids are used to switch the auxiliary 12-volt feed off when the ignition is off to allow your trailer's electrical hardware to run without draining power. This solenoid grounds onto your vehicles chassis..
Tow Ready 118665
Trailer Battery Isolation Solenoid, 3 Pole, 12 Volt (Chassis Ground)
Shipping Dimensions: 4.75 x 2.6 x 7.9
Shipping Weight: 0.8 lbs.