Megan Racing Down-pipes for the newer 2011+ BMW 1 series 135i (equipped with N55B30 Single turbo motor) are made of durable 100% T-304 Stainless Steel piping that is polished to a mirror-like finish. This Down-pipe replaces the OEM exhaust piping with all of its restrictive bends while increasing the inner diameter of pipe; this greatly increases exhaust flow and reduces turbulence within the system, as a result freeing up high-end horsepower and mid-range torque. Essentially the missing link to your exhaust system; this down-pipe will give you competitive edge that you have been looking for. Expect an increase in exhaust tone due to freed up exhaust flow. Specifications & Features: - 100% T-304 Stainless Steel Piping TIG-welded onto computerized CNC-machined flanges for strong, long-lasting durability -4" to two 2.5" collectors - Smooth bends improve flow and performance. - Fits 2011-12 BMW E82 135i Coupe, E88 135i convertible equipped with single turbo N55B30 motor only.