DC Sports HSR5523 Polished Stainless Steel 4-2-1 Header (2 Piece) Dyno tuned and tested against the competition for maximum performance CAD-rendered design with threaded flanges for easy installation 4-2-1 design emphasizes low and midrange power for street/strip applications CNC mandrel bends with robotically-welded fittings deliver perfect fit CNC machined flanges and O-ring seals eliminate leaks