Powerball

Bought a Powerball recently. Nice way to exercise my wrists and parts of my arms.

It is a gyroscopic toy sold commercially as a wrist exerciser device. It can be started with a short rip string or by a snap of the thumb. Once the gyroscope inside is going fast enough, a person holding it in his hand can accelerate the gyroscope to incredibly high revs by following a circular wrist motion with the device.