Exercise Ball 55 - 75 cmAdd Variety to Your Workout with the 55 cm 75 cm Gym Ball Too much sitting, too little movement that sums up the working day for most people. The consequences are foreseeable: Many people regularly suffer from back problems, tension and, as a result, headaches. An exercise ball is a great way to counteract this. It is ideal for strengthening your back and abdominal muscles. At Gorilla Sports, the colourful pilates balls are available in three sizes