Solid ZINC rotor provides a whopping 41.3 lb-in of resistance at 10,000 RPM * Stainless steel shell construction, anodized in silver color and polished to a mirror like shine for professional and amateur athletes alike. * Computer balanced inner gyroscopic rotor for VIBRATION FREE operation * Ideal for building muscle and grip strength for athletes. Combine with PB-588HC Spinner for BEST result! * Performance Digital LCD counter displays total revolutions in multiples of 100s, current speed in RPM, historical top speed in RPM, and a physical strength index that counts down in 30, 60, and 90 second intervals for a total number of revolutions in that duration