The Neptune LLS is a pioneering industry exclusive! With the ability to measure exact depths of liquid in both inches and cm, this continuous vertical sensor surpasses traditional counterparts & can be used in sumps, ATO reservoirs, AIO tanks, dosing containers, & more to monitor evaporation, consumption, and dosing levels. Data is displayed in both digital & animated form within the Neptune Fusion app, & Apex can be set to alert & take action whenever liquid levels change a specified amount. The potential this new tech offers for automating & optimizing aquarium systems is tremendous. Available in 4 sizes: 4", 15", 23", & 35".