The S-2 mounts under Standard Holley Carbs. Stop is 2" tall aluminum casting. Works well with gasoline or alcohol.
Exclusive Primary Adjustment allows you to tailor the ratio of primary to secondary blade angle with 3 adjustment holes. This is very important as it allows you to tune your CFM reduction to your combination (high gear stop, 2 Stage Timer, 4 Stage Timer, leave closed then open or leave open then close immediately).
Exclusive Stop Adjustment Knob is divided into 10 divisions (makes it easier to use throttle control programs from your weather computer because computers have trouble with "flats".) It also has a marker to let you know what "turn" the stop is set so you never lose track or have to measure.