The Wilwood Shutoff Valve blocks pressure from reaching downstream when energized. This Shutoff Valve is a single direction flow, allowing fluid to return to the master cylinder, eliminating the possibility of trapping pressure when activating the valve. This valve requires a 12 volt, 5 am fused power source through a toggle switch. The Wilwood Shutoff Valve is not designed as a line nock assembly and not for street use.