NSD Power Digital LCD Speedometer SM-02 for use with NSD Gyroscopic Spinner Keeps Track of Your Progress  Tracks your progress, speed and strength with the NSD Power Spinner with an easy-to-read digital LCD display with amber backlight Smart Display  Shows four different statistics, including current total revolutions, speed in RPM, historical top speed in RPM and physical strength index Easy to Use  Equipped with a handy auto-power function that turns it on at 3,000 RPM for easy tracking; Features battery-free design that generates power itself Simple Installation  Easy to install on your NSD Spinner; Works with Essential, Fluorescent, AutoStart and Metallic Series Spinners by NSD Patented Design  Designed and manufactured by NSD for the original NSD Spinner only; Beware cheap knock-offs and imitations