Reaction balls are designed to bounce in an erratic and unpredictable fashion and are used to help improve agility, hand-eye coordination and reaction time with these unevenly shaped balls that bounce unpredictably. Ideal for rehabilitation and cold hand drills. Great training tool for goalkeepers. Quick reflexes and reactions are vital to a lot of sports these days and with these reaction balls, now available from McSport, you can sharpen up for the game of your choice.A great training tool for all ball sports - use against a wall or with a partner. Features Reaction Ball. 9cm Diameter. A great training tool for all ball sports - use against a wall or with a partner. Quick reflexes and reactions are vital to a lot of sports these days and with these reaction balls. You can sharpen up for the game of your choice. Colour: Red. Size: Large - 9cm diameter . Weight: 160g.