This Live up LS3003 Weighted Balls are Iron Sand filled and can be used as a tool to develop arm strength, increase arm speed and promote arm health. They are excellent tools for providing resistance through the full range of motion in the arms. PVC weight ball filled with iron sand. Strengthen and tone muscles, hips, back, legs, arms and shoulders. Soft-to-the-touch surface. Compact and easy to grip, match hand size. More safe as ball will not easily bounce or roll. Helps tone muscle, improve flexibility and burn calories.