Dyno tuned perfection which add 25-30 rear wheel HP & 30-40 Additional FT/LBS or Torque (60rpm sooner in the RPM band). Constructed of T304 Stainless Steel these will go the distance. Additionally, this kit adds the Hush Power resonator. After many attempts and fitting dozens of resonators the Hush power by far is the best combination out there. The 409S HP-2 mufflers have a case length of 18-inches and a 4.00 X 5.50-inch width. Due to their Cool Shell Technology they can be placed in virtually any location under the vehicle. The 409S HP-2 mufflers feature a painted 409S outer shell, and 409S internal construction. 2.50-inch inlet/outlet diameters, there is a model available to suit your needs. The HP-2 line offers a wide variety of applications from rock crawling to award winning customs.