The TrolMaster WCS-3 Water Content Sensor 3 is specifically designed to measure the moisture level (in percentage) of the grow medium. The WCS-3 can be used with the TrolMaster Aqua-X (NFS-1), Aqua-X Plus (NFS-3), Aqua-X Pro (NFS-2), Hydro-X Pro (HCS-2) and Tent-X (TCS-1) control systems. Each WCS-3 sensor is a 3-prong Volumetric Water Content (VWC) sensor. To use the W CS-3, you will insert the 3-prong sensor into the grow medium such as coir , soil or rock wool to be measured. You can connect multiple Medium Moisture Sensors to a single controller. Up to 5 0 WCS-3 can be connected to the NFS-2 and HCS-2 controllers, 20 o n the NFS-3, 8 on the NFS-1 controller, and 1 o n the TCS-1 controller.