... 1, raw materials: the main material is cast iron, and some outsourcing is a layer of rubber ... the iron bar, both ends of the solid ball, because practicing without sound, named dumbbell. Light-weight ... The weight of heavy dumbbells 10,15,20,25,30 kg and so on. , ranging from circular iron plates, ... about 40 ~ 45 cm, 3.Benefits:Dumbbells can traine a single muscle; such as increased weight, ...