Allows you to change the amount of ignition vacuum advance for maximum part-throttle performance while preventing the harmful effects of spark knock (detonation). Dial in as much spark advance as conditions permit - add more advance under light load conditions to improve throttle response and fuel economy, or limit spark advance in high compression engines and high load conditions to eliminate knock. Built-in stop prevents the adjustment screw from "backing out" like other designs. Includes 3/32" Allen wrench and easy-to-follow instructions. Perfect companion to Moroso H.E.I. Advance Curve Kit No. 710-72300.