Sometimes you just gotta have the best of everything. When it comes to flow, you just can't get anything better than our Race Pro Muffler. This baby features a 'straight through' path that guarantees throughput that's 95% of straight tubing! The sound is surprisingly tame considering the absence of any impedance when you look down its barrel. At idle and low rpm cruising, you will not draw much attention, but upon acceleration, bystanders lookout! The Race Pros aggressive sound is the result of applying a layer of stainless mesh around a unique internal 3.5" louvered tube, accompanied by a healthy stuffing of basault insulation before the unit is sealed. Highly recommended for the track where every 1/10th counts. This 4" round version is also great for many street rod applications. Think of these mufflers as large inhalers for your engine. The welded case makes for a sturdy muffler that will not rattle. The stainless construction of our mufflers enables them to resist corrosion and extends the lifespan of the product, while their superior flow improves gas mileage. Pypes mufflers, when used as a Pypes system component, can be precision matched to deliver the ultimate in sound and performance.