COMPATIBILITY: Water Flow Sensor compatible with for Girard GSWH-2 Tankless Water Heater EXTEND HEATER LIFE: Replace old/ water flow sensors to extend the life of your tankless water heater and ensure proper operation of your hot water system FUNCTION: Water flow sensor measures the actual water flow and mits the data to the control board. The flow rate is determined by changes in frequency FUNCTION: The control board adjusts the heater output based on the water flow data provided by the water flow sensor to compensate for variations in water temperature NOTE: To confirm whether the water flow sensor is connected, check the water flow icon (a shower head symbol) on the UCP. When the hot water faucet is turned on, if the water flow icon is activated, the sensor is working correctly Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! Colour:Copper Color Material:copper Package Contents: 1 * Water Flow Sensor Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.