FloodStopper Valve, Switch and (4) SensorsThe Floodstopper single zone package is perfectly suited to most residential and basic commercial applications. This package comes complete with everything you need to keep your home safe from a major water leak, including the FloodStopper single zone controller, the actuator and shut off valve assembly, the 24 volt power supply transformer (plugs into standard electrical outlet), and 4 sensors two top terminal (gray) and two rear terminal (white).