Precision CNC machined billet nitrous manifolds install between the rubber carb boots and the cylinder head. Manifolds are tapped for any brand nozzle that has 1/16 NPT threads. Using APE billet manifolds make installing your nitrous kit a snap. Certain models feature o-ring sealing to the cylinder head. (GSXR 1100 shown) Sold in sets of four. Nozzles not included.