Bell-mouth for ET3 Polini air filter

This replaces the mounting ring of the polini air filter for vespa smallframe 19/19 carbs. The elliptical bell shape smooths and greatly increases the airflow. It will be required to rejet due to the much greater airflow. On our test bike we went from a 74 main jet to a 108. This design also has a serrated texture around the outside allowing the filter a much better grip.