Adding the optional APR Intake Filter completely transforms the APR Turbocharger Inlet System from subtle to extreme. Our massive 9" long cotton filter with frontal opening connects to a 6" carbon fiber inlet tube that gradually necks down to the 4" back tube. You will hear every ounce of the 5-cylinder turbocharger system's massive demand for airflow, and you'll do so at a 60% CFM improvement over stock! This was only possible with an open filter system as the airflow demands called for an unboxed design. Simply put, this is the best intake system on the market for satisfying uncompromisingly demanding airflow requirements.