This is just the module itself without sensors. The FMM (Fluid Monitoring Module) is a module that connects to ant Apex (Apex(2016), Apex Classic, Apex Lite, Apex Jr.) via it's AquaBus port providing 4 multi-function monitoring ports that can be used for flow sensors, leak detections sensors and possibly future products as well. The FMM has 4 ports where you can plug in various sensors and accessories (all sold seperately). The best part is that they do not need to all be the same type. Just plug them in and the FMM will automatically sense which type of sensor you have in each port.