Wilwood"s drive flanges are made from 7075-T6 billet aluminum then CNC machined to exact tolerances for precision fit performance. The billet material greatly extends the spline life for greater durability. It is available in a standard weight version and a light weight version. It comes complete with bolts and washers. "WARNING: This product contains a chemical known to the State of California to cause cancer and birth defects or other reproductive harm."