This is the hand-held trainer that uses centripetal force to simultaneously target arms, shoulders, back, and core, while remaining gentle on the joints. Trusted by professional athletes, it contains an 8 oz. precision steel ball that creates optimal resistance when rotating it around the resisted channel. The trainer is progressively challenging, fun, and only requires five minutes a day (in 30 second intervals) to help improve coordination and balance. Made with an aluminum frame, rubber channel, and padded handle. 12" Diameter. (3 1/4 lbs.)