The control knob mounts to the dash board for easy and accurate tim­ing adjustments up to 15°. The Control can be used on 4, 6 and 8-cylinder engines and must be used with an MSD Ignition Control. A dash-mounted control knob allows you to adjust the ignition timing to compensate for changes in altitude, low octane gas, or heavy loads. For cars driven every day but raced occasionally on the weekends, this control is perfect. Increased fuel mileage and performance are just some of the benefits as the ignition timing can be advanced or retarded to prevent engine detonation.