Injen Technology X-1021-BB 3.5" AMSOIL Ea Nano-Fiber Black and Blue Air Filter Removes 5 times more dust than traditional cellulose filter media alone and 50 times more dust than wet gauze filter media No oil needed for quick, easy setup and maintenance Built-in velocity stack to help speed up air through intake pipe Predetermined pleat size and quantity to ensure proper filtration and airflow rate Measures 2.75 opening, 5 base diameter, 5 height and 4 top diameter, 40 pleats