Our heavy duty and performance speedometers add dependability to your vehicle's information center. Our HD speedometers are 3 3/8" inch in diameter, the standard size for aftermarket speedometers and tachometers, unless otherwise noted. Odometers track how many miles the vehicle has traveled, and trip odometers are re-settable. Most of our speedos are lighted, with a built-in light bulb. Mechanical speedometers are driven by a physical cable, while electronic speedometers are powered by electrical current from a sensor.