Never before offered in the aquarium industry the LLS Sensors allow for the measurement of water depth in inches or centimeters. Available in four different sizes- 4″, 15″ 23″ and 35″ each sensor has a special place in helping understand the water level in the sump, aquarium, reservoirs, and other liquid-holding containers. No longer does one need to physically look to observe how much water level is above or below a specific point, but now simply open the Apex Fusion App and observe.