The present Recommendation applies to tungsten ribbon lamps used for the calibration of radiation thermometers (including visual or photoelectric tungsten ribbon lamps) and specifies the requirements for tungsten ribbon lamps subject to legal metrological control. The purpose of this Recommendation is to ensure that uniform calibration of these lamps can be carried out in all countries in a homogeneous manner with the accuracy specified hereinafter. The present Recommendation also specifies for these lamps: • Temperature measurement units; • Main technical characteristics; • Main parameters characterizing their metrological quality and the values of these parameters; • Main methods to ensure the uniformity of calibrations.