Thunder Heart Performance Thunderheart Programmable Speedometer Sensor EA4110 Used to correct your speedometer when you change tire size, pulley size, gear ratio or make any other changes that affect the speedometer Capable of 0-50% positive or negative correction Quick and easy adjustment with a push switch and built-in indicator light Includes OEM-style connector for easy installation on 96-03 models with electronic speedometer (except XL models) Made in the USA