iron-hoop rolling: 1.improve the balance of the body and the coordination of the eye 2.made of iron, 3.diameter 6mm,OD: 38mm iron-hoop rolling: 1.improve the balance of the body and the coordination of the eye 2.made of iron, 3.diameter 6mm,OD: 38mm Rolling iron hoop is a kind of traditional Chinese nationality children's game iron-hoop rolling