Sports Sensors Swing Speed Radar Small microwave Doppler radar sensor for measuring golf or baseball swing speeds Calculates clubhead or bat speed within a range of 20 to 200 miles per hour Positions about 8 to 10 inches from tee or suspends from a batting cage or net Transmission level is well within FCC requirements and prescribed safety levels Powered by 3 AA batteries; ideal for both players and coaches/instructors NOTE: Refer the Manual before use.