Large Three Layer Performance Air Filter:Momentum’s unique 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 oil-free Pro DRY S media with three layers of synthetic media for maximum convenience. Its progressive layering provides great filtration efficiency and dust holding capacity, while not requiring the use of oils. This media is best suited for street and light off-road use. Its inverted top makes for more filter surface area, resulting in longer service intervals.