The JLG 3990053 Tach Generator Kit is an aftermarket product designed for use with boom lifts. This kit includes a gauge and speedometer, making it a valuable accessory for those working with heavy equipment. With a shaft diameter of 0.19 inches and a total diameter of 1.2 inches, this kit is compatible with the JLG N40E model. The shaft length of 0.57 inches ensures a secure fit, while the two pins provided offer added stability and functionality. This tach generator kit is a reliable and essential component for any heavy equipment maintenance or repair project.