Bosu Trainer PRO Yakimasport Ball Properties: The BOSU ball is a simulator of movements typical of various sports disciplines. an ideal device for balance training a double-sided device that is a unique combination of a ball and a step the convex side of the device is a kind of working dome that bends with every movement of the exerciser the other side is flat, creating a rigid platform the device has two handles hidden in recesses the diameter of the platform is approximately 63 cm Color: blue black