Yunmai Wrist Ball do not need any power source, it keep running by the centrifugal force and consequently lead your wrist follow the turns, achieve exercise purpose.

Playing with unique start method
Yunmai has innovatively optimized the starting method, and have abandoned the traditional pull rope, so users can start playing with the wrist ball by simply pushing the arrow to the end and releasing it.

Mechanical power, no power supply required
The rotation of the wrist interacts with the inner rotating sphere, the centrifugal force generated by this action maintains the high-speed rotation of the sphere. As the wrist turns, the generated centrifugal force can keep the wrist ball running and consequently lead your wrist to follow the turns.