To take natural rain fall into consideration during controlled watering * For gardena water timer t 1030 plus/t 1030, water computer c 1030 plus/c 1060 profi/c 1060 profi/solar * Also fits controller 1250, irrigation control system 4040, flower box watering 1407; can be positioned in the soil or surface mounted * Optical/electronic operating principle, reacts quickly if it starts to rain * Uses 9-volt battery not included