This adjustable camshaft sprocket is a quick engine modification. It allows the camshaft to be adjusted 4.5 degrees advanced or retarded.  In the advance position it moves max torque down about 500 rpm, increases dynamic compression, and allows the engine to rev quicker. It improves the throttle response in the low to mid rpm range.  In the retarded position it will do the opposite and make more high rpm power at the expense of bottom end power.  Made from stainless steel.  Great for modified engines or engine tuners. Takes about 5 minutes to change.  Fits 2008+ XT250.