Large Five Layer Performance Air Filter:This 360-degree radial flow air filter features a 5" flange and our pre-oiled Pro 5R media with five layers of progressively finer cotton gauze media for maximum performance It provides your engine with the largest amount of high-flowing air and delivers the highest power gains in most cases. This media is perfect for street use. Its inverted top makes for more filter surface area, resulting in longer service intervals. The filter features an injection molded base and top for lighter weight and rigidity. Its base includes a built-in 3-angle velocity stack for smooth, even airflow and captive screws to easily attach the filter to the housing.