Franklin Sports MLB Speed Tracker Pro accurately records your ball speed. The wireless 2.4GHz technology transmits the speed of your ball to an LCD screen. The sensor easily attaches to most gloves, back stop, return trainer or chain link fence. Includes electronic pitch rubber with LCD screen, impact sensor with self-stick strap and retractable tape measure. Simply select 1 of 5 pitch distances; 24", 36", 46", 54" or 60.6". Measure the distance from the pitcher"s rubber to home plate using the tape measure. Attach the sensor to your glove or backstop, stand on the foot pad and watch the numbers blink; release your foot simultaneously with the ball release. When the ball hits the target the speed will register on the LCD display.