If you have an 06-11 Civic Si, this piece is for you. Mounted on the end of the fuel rail, this piece mates with the stock fuel line. It features an extended fitting to relax tension on the fuel line and help with clearance. Comes with an O-ring to prevent leaks. This fitting is included with the Hybrid Racing fuel line kit if you purchase it for the 06-11 Honda Civic Si. E85 compatible.