You want to know quickly what it is? Take a look at this video, it's the easiest mean of having an idea of it. Then come back if you need more precisions about it.

I'll try to tell you in few words every secret of a powerball. First, let's see how it looks like:

It seems really beautiful but it's not a decorative thing. It was created a few years ago by the NASA engineers to train astronauts in space. Here's how it works: You make the rotor spin by holding the powerball firmly in your hand and by moving it the same way a top moves after you started  it with a little string ( to gain enough speed ). You can now feel a force which can be weird at the begining but which is smooth , soft without any vibrations. To accelerate the rotor inside the powerball you have now to follow the same move the powerball generates in your hand. The strength applied on your wrist and arms grows slowly , what permits training. Regular training will increase the strength in yours arms, wrists and shoulders, you will also improve your performance in several sports like tennis, golf, and many others... The smooth, fluid action of spinning your Powerball when coupled to its inertia results in a unique therapeutic quality which will have a profound effect on Carpal Tunnel syndrome - CTS, Repetitive Strain injury - RSI, tendonitis, arthritis & all wrist related ailments while used for as little as just 5-7 minutes each day.

The huge success of Powerball is due to the fact that a speedmeter is assembled on it. It allows you to know how fast the rotor in spinning inside the ball. Thus, a world competition was born where it wasn't expected. Today, a lot of powerball players try to beat Akis Kritsinelis , a Greek who achieved an unbelievable highscore of 15840 rpm (rotations per minute!! May will Powerball become a known and official sport in the future...

Let's take a look at the several models available:
After the 250Hz pro blue we've seen upper, here is the 250Hz orange

This model with a speedmeter is recommended for people who would like to make competition.
Here are the 250 Hz Neon  models in green, blue and red:

Those models are really beautiful in the night because of their small LEDs built inside. The faster the rotor spins, the more the Leds shine. Recommended only for occasionnal users and light lovers. You will suffer from a handicap due to the fact that the LEDs take a part of the energy which is provided to the powerball, and because of a heavier rotor.

Eventually, here is the last model, the Powerball Techno 250Hz :

This model seems to be weird at first sight, but I think this powerball is not bad when you look at the design and originality of it. Indeed, you read your higscores directly on the rotor, by the light effect of a few leds built in it. It's really beautiful, but only recommended for very occasionnal users because of  its fragility . Don't use it for competiton because you can only prove your scores by making a video therefore it's not practical.
Finally you know now what's available on the market. Take note that every powerball exept the Techno are available without the speedmeter, they are called "regular". You can't see your performance with them. Every model can spin at speeds up to 15000 rpm ( and even more..) without vibrations. Moreover, few people can achieve highscores that exceed 14000 rpm.

There is still a model left that needs to be presented, but which isn't yet available. It's the future metal Powerball , called "Powerball Phantom 350 Hz" . You can already see how it will look like:

This new Powerball will be able to reach speeds of 21000 rpm and all without any vibration. It will certainly become the new competition model , and it will be less fragile that the plastic models. Warning: Other models of Powerballs ,or something that seems to be the same but with different names are available on the market. Don't buy them because they are not built with the same precision and quality as the real ones. Moreover there is no lifetime guarantee with them. Most of the time no speedmeter is built on it and their prizes don't exceed 5 $. Be careful!
A new type of speedmeter is to come. It will work with the bluetooth technology and it will allow users to see their highscore directly on a computer. It will also be possible to be connected with other users on the same computer. This speedmeter should be available in the next months.

Where can I buy a Powerball?