1. This float switch is a device used to sense the level of liquid within a tank,the switch may activate a pump,an indicator,an alarm,or other device. 2. Light weight and simple working principle,high reliability. It can be easily converted from normally open to normally close by invertin the float. 3. Use them with hydroponics, saltwater tank, freshwater tank, gardening, pet bowls, fish tanks, filtration, pumps, ponds, basement alarms, boats, air condition drain pans, aquarium, ice machines, coffee pots, marine,evaporator coils, Please Note: because the current that the switch can carry is much little(above 0.5A), you must use a relay or contactor when it is connected by a load, relay and contactor are not included here.