This Modulator Ring for Turbo Carbs installs where a velocity stack would usually go, and is a slightly smaller size than the venturi, which creates higher pressure above your main jets when you are under boost. Jetting usually needs to be leaned out after installation of these rings.

Fits Weber Turbo Carbs as well as Dellorto DRLA Turbo Carbs.

Also available in a 33mm size.