This Polini "Venturi" system is designed to increase air flow of your carburetor. Your old filter is removed and replaced with the venturi and a new air filter is installed at the front of the carb box and the air bellow is no longer used. It requires at least a 10 point jump in main jet size but does require tuning of your other jets as well depending on your engine set up. 

**Lock tight is highly recommended on the bolt holding the venturi to the carb to prevent it from coming loose and going down into the crank case.**