The T-304 stainless steel materials are known throughout the industry as the highest quality for aftermarket exhaust, *Using the latest machinery all tubing is CNC mandrel bent for precise fit and uninterrupted exhaust flow for better performance *Mufflers and tips are hand polished to a mirror like finish like no other system on the market, *Uses engine vacuum for ample supply to close valves when so desired, *Limited Lifetime warranty, *50 State emissions legal, Each of the mufflers has two outlets, with one side having a butterfly valve which allows the exhaust flow to be shut off regulating which side of the muffler the flows exhaust. One side of the muffler is the "quiet" side, and the other is the "loud" side. The "quiet" side is a smaller, muffled and chambered tube, while the "loud" side is 3" tubing straight through.