Exhaust Valve: This axle-back exhaust system incorporates a factory style exhaust valve which uses the factory exhaust valve motor (not included). The valve helps regulate, direct and control the flow of exhaust gases by opening, closing, or partially obstructing passageways depending on throttle position for maximum performance. Simple Installation; This MACH Force-Xp axle-back exhaust system uses factory mounting locations providing stability and a hassle-free installation. Dual 4" Gloss Black Tips; Finishing off thi s system are dual 4" diameter, gloss black, 304 stainless steel tips. The tips come with a laser-etched aFe power logo for an aggressive style. Leak-Free Seal: High quality band clamps are used for a complete 360 degree sealing surface. Brushed 304 SS Construction: The performance axle-back exhaust system is constructed of 3" to 2-1/2" mandrel-bent, brushed 304 stainless steel tubing for maximum performance, corrosion resistance and strength eliminating cracking. MACH Force-Xp Axle-Back Stainless Steel Exhaust System w/Polished Tips BMW 340i/iX 440i/iX (F3X) 16-18 L6-3.0L(t) (B58) BMW 340i/iX 440i/iX (F3X) 16-18 L6-3.0L(t) (B58)