The Powerball is a Human-Powered Gyroscope!! 

 "The World's Fastest and most Powerful Hand-Gyroscopes..."

About the size of a tennis ball, the Powerball is a handheld exercise device, standing proud as the most revolutionary hand strengthener and conditioner ever invented. Within one week of using a Powerball you will actually feel new strength in your hands.
The Powerball is ideal for strengthening or rehabilitating muscles in the fingers, hand, forearm, upper arm and shoulder.
Powerball has excellent treatment and therapeutic uses for Arthritis, Carpal Tunnel Syndrome, Tennis/Golfers Elbow, Repetitive Strain Injury and other similar ailments/conditions of the arm and extremities.

 TORQUE ABOUT SPEED !!! 

Work and Play! This remarkable human-powered device is a ton of fun to use. The incredible speeds you can push it to and the amazing torque it delivers make for a potentially addictive device - coupled with the fact that you can really feel it testing your strength and endurance... it's all good!! ... and guaranteed to keep you going back for more punishment. The Powerball PRO models have a multifunction Speedometer which absolutely multiplies the functionality, fun and addiction factors by many times.

Don't let imitations confuse you!, the Powerballs you see in these pictures are the official 'Worlds Fastest and most Powerful Hand-Gyroscopes'. Hand-assembled and finely tuned to deliver the smoothest and fastest gyroscopic action money can buy!