The hand enhancement ball is the centrifugal force generated by the interaction between the rotation of the wrist and the internal rotating core, which can maintain the high-speed rotation of the core, promote blood circulation, and increase the fingers, wrist, hand, forearm, biceps, triceps, and ligaments And the strength of the shoulders, restore muscle strength.☞☞ Product DetailsProduct name: wrist ballInner ball material: zinc alloyShell material: polycarbonate, siliconeThe product contains: wrist ball*1(not including other things)☞☞How to use:1. Push the thumbs of both hands in the direction of the arrow of the center of the ball until the resistance is large and the center of the ball cannot roll.2. Quickly release the core of the ball with the thumbs of both hands, and turn the ball by the hand3. After feeling the sphere rotates, swing the ball from left to right in a circle-like way to slowly rotate the wrist ball, and the speed can be increased with the inertia☞☞Notice *1. Not suitable for children under 10 years old whose hand strength insufficient to use the product *2. Do hot drop it from high or hit it on hard objects, it may cause serious damage *3. Do not touch the inner ball while it in high-speed running *4. Do not add any oil or moothy liquid into it which may cause it inoperation ☞☞ Service:1. If you need more styles, please click our other products to find the style you want.2. If you have any questions before or after your purchase, please do not hesitate to contact us.