It allow you to adjust the amount of ignition retard from 1 deg per pound of boost to 3 deg per pound via a control knob that you mount on the dashboard. This way you can make adjustments on the fly to prevent detonation as fuel quality or altitude and air quality changes up to a maximum of 15 deg retard. You can also set a boost pressure point to start the retard. There is a boost pressure port to connect to your manifold and the BTM wires easily to the MSD Ignition Control. Adjust the timing from the drivers seat. Easily connects to your MSD Ignition. New feature allows you to set a boost pressure point to start the retard!