Crossover headers offer easier fit and less upper engine heat that 180's. With the correct pipes, crossovers are unrivaled in performance. Each segment of an exhaust system works in combination with the engine and the rest of the exhaust system. That is why we offer a selection of diameters with primary length flexibility. The final 4" of the 36" primaries are made in parallel to allow you to change the length before attaching the slip-on collector. All crossover headers have 3/8" thick CNC flanges.