The Neptune Systems Liquid Level Sensor (LLS) is a precision device designed to monitor and measure water levels in aquariums or sumps as part of the Apex system. It utilizes patented resistive sensing technology, allowing for accurate measurement down to two-tenths of an inch once calibrated. The LLS sensor includes a mounting clip that attaches securely to the side of your sump, aquarium, or container, ensuring easy installation even on euro-braced setups. This product is ideal for advanced hobbyists and reef tank owners who need precise water level monitoring without immediate control requirements like auto top-off.