These 360-degree radial flow air filters feature a 4" flange and our oil-free Pro DRY S media with three layers of synthetic media for maximum convenience. Their progressive layering provides great filtration efficiency and dust holding capacity, while not requiring the use of oils. This media is best suited for street use. The included massive air filters are surrounded by open-element XLPE (cross-linked polyethylene) polymer housings that minimize warm engine air for maximum performance. Their open design allows for easy viewing of their air filters and delivers an aggressive Air Intake sound. In addition to the system's built-in air inlets, optional Dynamic Air Scoops (sold separately) are available to bring more cool air from the front of the vehicle into the intake housing (PN 54-12489-C).This system features high quality, computer-designed, dyno-tuned intake tubes to achieve maximum power gains while maintaining a perfect fit. Their XLPE material is heat soak resistant and extremely durable. This is a direct fit intake system that utilizes factory mounting points and requires no cutting or modifications. All necessary clamps, couplings, and hardware are included. Its revolutionary design, featuring our patent pending filter-to-housing interface, uses half the number of parts of a traditional cold air intake system.