For use with vantage pro, and vantage pro2. (Already included with vantage pro plus and vantage pro2 plus.) measures solar Radiation and is required (along with an anemometer and a temperature/humidity sensor) if you wish to monitor evapotranspiration. Diffuser element and housing are carefully designed for accurate cosine response. Silicon photo diode provides good match to solar spectrum. Two-piece housing minimizes Radiation heating, allows convection cooling of the sensor, and prevents the trapping of water or dust. Includes built-in level and 2 (0.6 M) cable. Available for sale in the United States and Canada only.