This cat-back exhaust system is constructed of 3 IN - 2-1/2 IN mandrel-bent 304 stainless steel tubing for maximum strength and durability. This system features a high-flow stainless steel muffler, producing a mild sound. Muffler finish may vary. Finishing off this exhaust system are quad 4 IN diameter carbon fiber 304 stainless steel clamp-on exhaust tips. The tips features an aFe POWER logo for a unique style. This system produces an aggressive sound unleashing all available horsepower and torque. Some cutting may be required, see instruction sheet for further information. Utilizing factory style hangers this system mounts directly to factory mounting locations for a hassle-free installation. A mitered merge x-pipe is used to balance and evenly distribute exhaust pulses traveling through the exhaust system, minimizing exhaust drone and maximizing scavenging. This system incorporates factory style exhaust valves which use the factory exhaust valve motors (not included). The valves help regulate, direct and control the flow of exhaust gases by opening, closing, or partially obstructing passageways depending on throttle position for maximum performance. State-of-the-art computer-aided design technology is utilized for precise vehicle fitment. 100% TIG-Welded for race-proven strength and durability. MACH Force-Xp 3 IN to 2-1/2 IN Stainless Steel Cat-Back Exhaust System Carbon BMW M4 Competition (G82) 2021 L6-3.0L (tt) BMW M4 Competition (G82) 2021 L6-3.0L (tt) Fitment: 2021 BMW M4 Competition