Exercise balls are also called Thai Ji Balls, Healthy Ball or Therapy Balls. They are dated back to Ming Dynasty. They comes from the ideal of traditional Chinese medicine. Through fingers moving, the function of brain and internal organs can be strengthened, so as to help blood circulation and to remove fatigue. Putting two balls in one hand and rotating can relax mind and hand. It is good for releasing pressure.

Two balls can produce nice sound and they are included in one box.
made of metal
Color will be different from the one shown here.