Dragster racing technology. The venture (funnel-shaped) air ducts optimize the airflow to the carburettor and accelerates the volume of air being taken in. The funnel is simply attached to the carburettor where the filter normally sits. A lightweight, metal filter is included, but is not essential to use. We recommend this item for sprint races or show purposes. The filter action is not sufficient for general everyday use. The clamp allows you to adapt the sizing by +/- 2mm. You receive 1x 42mm intake funnel with clamp ring and filter.