K&N Air Filter KRK-3944K&Ns Street Metal Series High Flow Air Intake Systems provide attractive styling, offer increased airflow and deliver more horsepower & torque to your Harley Davidson motorcycle. These air intake systems eliminate the stock OE air cleaner and replace it with a complete high flow air intake system to increase power. The sturdy, custom aluminium backing plate mounts directly to the throttle body via an aluminium integrated, internal run breather system.