Reflex ball is made of solid, durable, high-density rubber and consist of a Six-hemisphere design creating dynamic and unpredictable bounce. It is great for all hard surfaces including grass, wood, asphalt, clay, even dirt.reaction balls give you the perfect analysis of your players engagement with the ball as you get immediate feedback on their reaction time. This six-sided high-bounce rubber ball leaps and pops randomly, keeping players on their toes.