This is the SFR QFT(Quiet Flow Technology)cat-back system for the 951.The SFR QFT cat-back system utilizes our highest quality mandrel bent 304 stainless steel tubing, factory hangers, flanges, etc... These SFR 3" cat-backs utilize a specially designed muffler. This muffler features a single 3" inlet which splits into dual 2.5" chambers and merges back into a single 3" outlet. This muffler flows as well as any straight through 3" muffler but the noise level is much quieter then any other muffler on the market today.The sound of this system is very deep.