This Flowmaster® Flow FX® cat-back exhaust system for the 2020-2025 GM 2500HD/3500HD trucks with the 6.6-liter gas engine is manufactured using durable 409 stainless steel throughout and features 3.50 to dual 3.00-inch mandrel bent pipes for better exhaust gas flow, and a Flow FX "straight-through" muffler is used for a moderate sound level and maximum performance. Maximum increases on the dyno revealed +9 hp and +10 lb-ft at the rear wheels. This system exits out both sides, behind the rear wheels with 4.50-inch black ceramic tips for added style and a custom look. The system uses all the existing factory hanger locations and includes installation instructions and all necessary hardware for an easy installation that you can do at home. Backed by Flowmaster's Lifetime Limited Warranty.