They seem to be only pipes: but the real thing is different. Made in AISI 304 stainless steel and, for Competition systems, in titanium alloy, Header pipes kits you can buy from an Arrow dealer come from an hard development, done by Arrow R&D guys, using all the experience made up in years of work done in worldwide race-tracks. To this extremely important ingredient, you have to add the craftsmanship of Arrow R&D people: pipes diameters, sections changes, components, welding and layout are carefully tested to design a product with high performances, reliable, long-lasting and, last but not least, good looking. Depending on the engine and on the ignition scheme, the best layout is choosen for the header pipes, the manifold and the mid-pipe, up to the silencer(s). So we speak of 4:2:1, 4:2:2, 2:1:2, 4:2:1:2, 3:1:1 and so on: all this stuff may seem too close to a football team playing tactics, instead the right choice for the header scheme is a key factor to have a good designed full system. Theory is not enough, we need also a superior attention in the production process: it's extremely important to keep the sections changes as smooth as possible, to have a gas flow that is the most regular as possible. To meet this goal, junctions between the various parts of the full exhausts are made with CNC machined components. For the same reasons, weldings have to be almost perfect and cannot reduce the gas flow sections.