1、Smart Display: The wrist ball allows for real time monitoring of exercise duration, speed, and precise strength. Has summary, time, and power modes for a diversified workout. 2、Versatile Use: The wrist bones strengthener ball is suitable for exercising arm strength, wrist power, chest and back muscles, both at home or at the office, catering various needs. 3、Unique Design: The wrist exercise ball operates on the principle of centrifugal force, the faster the speed, the higher the required opposing force, helping build strength progressively. 4、Accurate Sensing: Using Advanced speed sensing technology, the forearm trainer ball accurately records each exercise's duration and changes in strength, allowing for scientific planning of training intensity. 5、Ergonomic Design: The curved handle design of this muscle strengthener ball excellently fits wrist curve and can be securely held even under high intensity vibrations, ensuring safety and comfort during workouts. Item Type: Wrist Trainer Ball Material: ABS Battery Quantity: 2Pcs (Ship with Built in Battery) Single Battery Capacity: 65mAh 1 x Wrist Strengthener Ball 1 x Instruction Manual