Large Five Layer Performance Air Filter: Momentum's innovative filter-to-housing interface was built to feature the largest air filter possible. This 7-1/2 IN tall 360-degree radial flow air filter features a 3-1/2" 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 and/or track use. Its inverted top makes for more filter surface area, resulting in longer service intervals. Unique One-Piece Housing: The smooth one-piece sealed housing, constructed of heat-resistant cross-linked polyethylene (XLPE) polymer, features our patent-pending filter-to-housing interface. Its innovative design minimizes the total number of parts, making for an easy installation. A large, clear sight window allows for hassle-free filter inspection, without having to disassemble your system. The system captures cool air with an included Dynamic Air Scoop at the front of the vehicle and an additional air inlet in the vehicle's fender well. Dyno-Tuned Intake Tube: This system features a high quality, computer-designed, dyno-tuned intake tube to achieve maximum power gains while maintaining a perfect fit. Its XLPE material is heat soak resistant and extremely durable. Hassle-Free Installation: Stainless-steel clamps and silicone couplings are included for strength and durability. Momentum intakes are designed with fewer parts for a fast and easy installation. Takeda Momentum Cold Air Intake System w/ Pro 5R Filter Subaru WRX STI 18-21 H4-2.5L (t) Subaru WRX STI 18-21 H4-2.5L (t)