Top quality machined billet aluminum construction. Works with all OEM# or aftermarket flywheels including S&S®, from 1938 Knuckleheads to the 1999 EVO Motors. Fixture clamps into vice For ease of use. It simplifies all assembly jobs while getting flywheels close to true before the final truing process. Helps hold flywheels in line for tightening of the tapered shafts.