Super Stock IRF Pro DRY S Air Filter (31-80011) by aFe. The Super Stock IRF Pro DRY S Air Filter can increase airflow to your engine by 90Percent, with up to 65Percent greater dust holding capacity�without changing anything else in your air intake system! The unique inverted design of the IRF provides up to 76Percent more filter surface area, for increased airflow and dust holding ability. The IRF is by far the quickest and easiest way to give your engine more airflow and protection.