Get accurate readings from your speedometer with one of these optional tools available from Classic Instruments. The “Sky-Drive” sending unit utilizes GPS technology to program and calibrate your speedometer. Mount this compact and lightweight unit anywhere and with the push of a button, you can set your speedometer up for miles per hour, kilometers per hour and more. The signal interface model converts the electronic signal from your transmission to an accurate speed-reading using either and 8,000 or 16,000 rpm signal. Set your speedometer with a pushbutton and calibrate with the mile-marker method. Each interface model features a 12-volt power source, which helps eliminate interference. Each unit comes with complete directions to provide a hassle-free installation experience.