sand-filled ball fine sand filling smooth sand ball fitness muscle exercise gravitational ball sand-filled ball 灌沙球 细沙填充光面沙球健身肌肉锻炼重力球灌沙球

This solid ball sand toy offers many advantages. Its outer layer is made of soft PVC material, which is comfortable, skin-friendly, has a good feel, and is non-slip. The interior is filled with iron sand, ensuring even weight distribution. The ball can be inflated, allowing flexible adjustment of hardness and size, making it suitable for various training scenarios. Additionally, it is safe and durable, unlikely to cause injuries, easy to maintain, and highly cost-effective.