Product Name: Portable Wrist Ballshell Material: Absinner Core Material: Zinc Alloysuitable Age: 10 Years Old +function: Wrist Exerciseproduct Weight: 300gproduct Size: 70*70*55mmautomatically Start, Follow The Arrow To Push To The End, Let Go Of The Ball Core And Start Easily.internal Metal Ball Core, Optimized Clockwork Structure, Smooth Operation And Low Noise.high-speed Rotation, Effective Exercise Of Wrist And Arm Strength.the Anti-falling Lanyard Design Prevents Accidental Falling Off Due To Too Much Inertia, Making It Safer To Use.cool Lighting Effects Increase The Fun Of Sports.the Working Principle Of The Wrist Ball: Using The Principle Of Gyroscope And Celestial Mechanics, Under The Action Of The Law Of Inertia, It Continuously Rotates And Generates Strong Force, So That The Wrist And Arm Are In A State Of Autonomous Movement. The Powerful Force Generated By The High-speed Rotation Of The Wrist Ball Is Very Helpful To Exercise The Strength And Toughness Of Our Fingers, Wrists, And Arms.instructions:1. Wear The Lanyard And Push The Thumbs Of Both Hands In The Direction Of The Arrow Until The Ball Core Cannot Roll;2. Let Go Of The Core And Hold The Wrist Ball With Your Hands;3. After Feeling The Sphere Rotates, It Swings Left And Right Or Swings In A Circle, Feels The Strong Inertia, And Effectively Exercises The Strength Of The Wrist. (the Faster Your Wrist Swings, The Stronger The Inertia)"All our products have undergone strict quality inspections. If there is any quality problem or you are not satisfied with the product contact us. We will give you the best solution. ""