Required for the XR150L when using the big bore kit.  This carb is 4mm larger than stock and includes an adjustable accelerator pump.  The 30mm carb is much larger than the OEM intake manifold, so it requires port matching on the carb side of the intake manifold.  Other requirements are: free-flow exhaust and airbox flow improvements.  Makes a huge difference when paired with the larger displacement engine.  Comes with throttle cable.