The 75920 Cole Hersee master disconnect switch from Peerless Electronics has a capacity of 300 amps at 12 volts DC. Designed to protect vehicles against tampering, theft and battery drain, the switch can be used in positive or negative path applications. Waterproof and dustproof to IP67 (immersible), the switch is made from engineering grade plastic. The large divider on the base prevents accidental shorting. 800/285-2121; www.peerlesselectronics.com.