Second post guys so please go easy
I've been looking at these for a little while, this seems to have come down in price again, just ordered mine. I think its one of the cheapest prices on the internet, on play.com its £24.99
Below is some literature lifted from Amazon.co.uk
Powerball is the world's most powerful hand gyroscope, generating speeds of over 16,000 rpm! Simply by starting up the Powerball in your hand and rotating your wrist faster you can develop incredible speeds and increase your strength. Powerball is seriously addictive for all ages, making it ideal for play, exercise, or fun competitions.
Powerball is a dynamic and completely revolutionary new gyroscope that literally explodes with mind-numbing torque and inertia once you activate its internal rotor.
It's about the same size as a tennis ball and weighs just a little more, but take a Powerball in your hand, set that rotor in motion with the cord provided (or use your finger when you get used to it) and you'll experience an extraordinary sensation. Powerball slowly comes alive with gyroscopic force - a sublime yet pleasant resistance to your movement which is transmitted directly into your wrist and arms and which provides soothing, non impact rehabilitation at these lower speeds.
Bring your new Powerball up to 10,000rpm, the forces are now much stronger, much more vibrant. Higher! Take it right up to an unbelievable 15,000rpm at which point it's exerting almost 40lbs of pressure on your limbs and is travelling at nearly 250 revolutions per second. No batteries, no motor, just pure gyroscopic power