FlowFX Muffler - 2.50 In/Out - Round Body - Moderate Sound - Stainless Steel; Flowmaster s FlowFX series mufflers are for the enthusiast who is looking for an economically priced performance muffler that delivers a moderate sound level and tone both inside and outside the vehicle. The large straight-through smooth core offers up a different sound than that typical chambered sound that Flowmaster has become famous for. These new FlowFX mufflers have a compact 4.00 inch diameter round body that will fit nicely on just about any application and feature a fully welded 409S stainless steel case for increased durability.;