This is a SF-R PT100 high temperature sensor. It is a high quality plantinum thermistor with a range between -50C - 350C, meet the most reuqest of temperature application. It is used as the Overlord temperature sensor. The resistance value it reads inside the nozzle is fed to the mainboard which converts the raw data in to a temperature reading. The printer can then adjust the temperature of the nozzle. It is compatible with both the Overlord and Overlord Pro.