The HYDROS Water Level Sensor is an optical sensor you can use for a variety of aquarium applications, such as sensing when your tank needs to be topped off or to detect when a dosing container needs a refill. It plugs into any Sense Port on a HYDROS device (like the Control 2 or Control 4) and does not require any additional power source. HYDROS Water Level Sensor Specs: Size:Diameter - 0.75” Sensor - 0.55” thickMagnet Mount - 0.25” thickCord length - 98" Max Mounting Thickness: ½” Use as High or Low Level No Moving Parts Magnetic Attachment For freshwater and saltwater aquariums The HYDROS Water Level Sensor uses a GX12 aviation-style connector so that the Control can maintain its IP65 rating (dust-tight and protected from water spray at any angle). Powered, monitored, and controlled by plugging into a Sense Port on the HYDROS Control. Manufactured by AutoAqua, an official HYDROS Technology Partner.