please buy it from this links if you want to buy black circle as below :
http://www.aliexpress.com/store/product/new-style-Power-Gyroscope-LED-Wrist-Strengthener-Ball-SPEED-METER-Power-Grip-Ball-Power-Ball-china/708547_803608061.html
Description:
how does it work?
The high performance internal gyroscope reaches up to 10，000 rpm and is set in motion by a cord. All you need do is to increase the speed by making a rotational wrist movement and to keep in sync with the spinning of the ball. (Don't worry， you can see the picture)
Features:
1.The illuminated LED wrist ball is the latest must-have for all fitness fanatics.
2.Whilst strengthening fingers， wrists， arms and shoulders it is also beneficial in increasing co-ordination and blood circulation.
3.The faster you spin the harder your muscles work - and when you spin the LED lights inside the ball will illuminate.
4.All you need do is to increase the speed by making a rotational wrist movement and to keep in sync with the spinning of the ball.
5.Roller ball doesn't need batteries， is only slightly bigger than a tennis ball and doesn't weigh much more， making it easily transportable for on-the-spot fitness whenever and wherever you are.
6.internal LED bulbs light up when the ball is in motion
colours :black ，red ， purple， orange ， green ， blue
