When looking for quality, performance and value in a bolt-on 5.0 liter header kit, the 1-5/8inch tube diameter allows for a perfect match with all levels of performance. The distinctive quality of the CNC machining guarantees many years of enjoyable performance. Fully Mandrel Bent Heavy-Gauge Tubing One Piece Laser Cut Flanges Eliminates Flange Warping CNC Machined Aluminum Alloy Direct Bolt-On HP & Torque: 15-20 HP/20 ft lbs Torque Installation: Direct replacement of the stock exhaust manifolds, header bolts up to the existing stock Y-Pipe/Crossover pipe. No cutting or welding required. Takes between 3 And 6 hours depending on application. Only simple hand tools required All hardware, gaskets, and instructions included.