Note: This item is with speed counter and led light， packed well without retail boxColor: blue as the picture showedMax Speed: 12，000 R.P.MWrist ball doesn’t need battery， it is powered by rotating the wrist， all you need do is to increase the speed by making a rotational wrist movement and the speed of rotation can reach up to 12，000R.P.M. The faster you spin the harder your muscles exercise. Function1. Perfect exercise gadget for sports like golf， tennis， squash， cricketm badminton， baseball， bowling， basketball， motocross， mountain climbing.2. Increases strength in fingers， wrists， hands， forearms， biceps， triceps， ligament and shoulders.3. Great benefit for musicians， guitarists， pianists， drummers.4. Rehabilitates sore muscles and joints.