Fitness ball, also known as gravity ball and fitness ball, has a standard size of about 14 inch. For men, the weight is usually 3 kg; Female 2 kg. It is usually used to help patients with injury recovery, rehabilitation and strength training. It plays a very important role in sports medicine. Nowadays, fitness balls are becoming more and more popular all over the world, even in China. However, people sometimes confuse fitness balls with larger ones.