Harley performance air cleaners for sale. SMT Wheels uses an S&S air cleaner made of high-quality billet aluminum and bolt-in parts with a reusable K&N filter. The air cleaner cover will match your custom SMT wheel design and fit your specific Harley like a glove. S&S air cleaners improve performance because the K&N filter is exposed for better airflow to add horsepower to your motorcycle.