Axial Engine Carburetor Insert Set (6.5 7.0 8.0mm) Aluminium.

This is an optional Axial Aluminum Carburetor Insert Set, and is intended for use with the Axial .21RR-1 .21 engine. The carburetor venturi is used to adjust the airflow that is allowed into the engine. By changing the size of the venturi, you can fine tune the power delivery and run time of the engine. A larger venturi will increase top end power, while at the same time reducing run time. A smaller venturi will improve bottom end throttle response, and improve run time.