MSD Adjustable Timing Controls # MSD8680Timing Controller, Analog, Adjustable Timing, Programmable, Each Circuitry:AnalogControls Ignition Advance:YesControls Ignition Retard:YesController Activation:ProgrammableAdjustable:YesAdjustment Style:KnobIgnition Box Required:YesCompatible with Multiple Coil Ignitions:NoQuantity:Sold individually.Special Attention:Must be used with a MSD ignition control. MSD Adjustable Timing ControlsChange your vehicle's ignition timing without leaving the driver's seat with one of these MSD adjustable timing controls. They're designed to fit virtually all vehicles with a 12 V negative-ground ignition, a distributor, and an externally mounted coil. They feature a knob that mounts to the dash for easy and accurate timing adjustments, allowing you to adjust timing up to 15 degrees to compensate for bad gas, altitude changes, and heavy loads.