Specifics and Features: 1-5/8" OD Primaries 3" OD Collector 3" OD to 2-1/2" OD Weldable Collector Reducers 100% brand new, Never been tried or installed TIG welded CNC Machined Flanges Long Tube Headers, Flange Connections Metal Gasket Included 2 X 4-1 Racing Design Increase high flow air, instantly gain 10 to 15 Hp. / Tq. Fitment?? .