Features: - Simple to start with a pull-string. - The faster you spin the harder your muscles work. - Internal LED bulbs will light up when the ball is in motion. - Small, compact and transportable, you can take anywhere. - It is powered by rotating the wrist and the speed can reach up to 12.000RPM. - Rehabilitates sore muscles and joint, great for musicians, guitarists, pianists, drummers. - 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. - Strengthen fingers, wrists, hands, forearms, shoulders and bicep etc., and also be beneficial in promoting co-ordination and blood circulation. Specifications: Material: PC + PP Size: 7cm(Dia.) I Package list: 1 * Wrist ball Notes: 1. Manual measuring, please allow 1 ~ 3mm error, thank you. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. We guarantee the style is the same as shown in the picture.