Large Five Layer Performance Air Filter:This 360-degree radial flow air filter features 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, usually resulting in the highest power gains out of all our filter media options. This media is perfect for street and/or track use. Its inverted top makes for more filter surface area, resulting in longer service intervals.