Dynomax 17221 Ultra-Flo Welded Muffler Stainless steel construction for lifelong protection 100% welded design for maximum durability Straight through design ensures unrestricted exhaust flow and reduces back pressure CRF Technology absorbs unwanted interior resonance while maintaining a deep performance tone Dyno proven to flow up to 2,000 SCFM and support up to 2,000 horsepower.