It is necessary to buy. Wave speed ball is a kind of spherical fitness equipment, also known as BOSU semicircle balance ball. It consists of two semi-circular spheres, which can be used for various fitness training. It can help to exercise the whole body, and at the same time, it can train different surfaces, such as the core stability training of the spherical surface or the balance stability training of the bottom surface. In addition, the wave speed ball also helps to improve the sense of balance and coordination of the body, and is also very beneficial to prevent accidental falls and other problems.