For Mustang/Fairlane/Cougar V8 Stainless Steel Long Tube Header/Exhaust Tubular Manifold Made of High Quality T-304 Stainless Steel with Computerized Mandrel-Bends for Strength and Durability i.e. Maximizing Smoothest High Exhaust Air Flow Rate 2 x 4-1 High Performance Racing Spec. Design, Produces the Most Top End Power Offers the Best Flow Characteristics for the Engine at High Engine Speeds Increase High Flow Air, Instantly Gain 10 -15 Hp. / Tq. Inlet/Outlet: 1-5/8"(OD) / 3"(OD) / 10mm Thick Header Flange / 3" to 2.5" Exhaust Collectors Included