The Steinel HL Scan measures the temperature of the workpiece surface whilst working on it with a hot air tool. An acoustic signal sounds as soon as heat either exceeds or falls below the ideal temperature. Its display also shows whether the workpiece surface is too hot or too cold. Red means too hot, green means ideal temperature and blue means too cold. The HL Scan can be fitted to hot air tools HL1920E, 2020E, HG2120E and HG2320E. The warning tolerance range can be selected to suit individual needs. If chosen, the visual and acoustic warning can be deactivated. Temperature Measurement Range 0-300C Optimum Distance From Workpiece 15cm Battery 9V (supplied)