... : 6pcs a grade LED Item No.:868N Product naem:Wrist ball with LED Description:Sheel material: A GRADE PCRoller material: Zinc ... battery or electricity inside the device, it is powered by rotating the wrist, and the speed of rotation can reach over ... for sports like golf,tennis,squash,cricket,baseball,bowling,basket ball,motocross,mountain climbing.-Increase strength in fingers, wrists,hands,forearms ...