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