1. Case material: polycarbonate, silicone (anti-slip ring) 2. Material of ball core: stainless steel 3. Uses: decompression, fitness, entertainment and other ways to play 4. Controlled strength, increased entertainment, with variable speed lights (optional) 5. Take wrist rope protection to prevent the ball core speed from flying out too fast, easy for safety 6. Feel the force of the shaft with the wrist, which can exercise the finger muscles and coordinate yourself 7. Built-in autonomous elastic device, play at any time 8. Weight: 270 grams 9. Size: 70x70x55 mm