The IAG Unequal Length Headers are the perfect way to add more performance to your Subaru WRX STI and still keep the iconic "Boxer Rumble." The headers are fully constructed of 304 stainless steel, including cast stainless flanges! The unequal length headers feature a 45mm pipe diameter for maximum flow and performance. Due to the free-flowing design of this header, you will see gains across the entire RPM range, as exhaust flow is vastly improved. The header also features a slip-joint expansion section to accommodate for flex caused by heat cycling. Each IAG header is fully TIG welded for maximum strength. Each header package includes the IAG 60mm uppipe that utilizes a 3-bolt cast flange and multi-layer gasket between the manifold and uppipe, providing a stable connection without exhaust leaks. The IAG Header & Uppipe adds all of the hardware and high quality, multi-layer gaskets needed for installation including specialty copper exhaust nuts, which are proven to maintain their torque even in the extreme conditions of heat cycling present at the exhaust flange.