Large Five Layer Performance Air Filter:Momentums innovative filter-to-housing interface was built to feature the largest air filter possible. This 7-1/2 tall 360-degree radial flow air filter features a 4″ 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.