The Speedometer Calibrator Module connects in-line with the factory wiring harness behind the dash. The Module comes with a USB cable and software that lets you dial in tire and gear changes before installation. The Calibrator Module doesn’t disrupt any OE diagnostic or safety systems, and allows for tire and gear changes for vehicle models that can’t be calibrated through the factory computer, or for tire and gear combinations outside of the ranges that are programmable. Features for the In-Line Speedometer Calibrator include Tire Size: No Limit; Gear Ratio: No Limit; Corrects speedometer reading; Corrects odometer signal; Includes CD with instruction manual and Tire Configuration software; FREE Shipping!