Mandrel Kit, which is made specifically for use with Allstar ALL31030 Crank Pulley, prevents mandrel bolt breakage. Mandrel is attached to the crankshaft pulley with three stock length bolts while the vibration damper is retained with the stock bolt. The mandrel bolt is then connected to the mandrel - not to the crankshaft - to reduce the possibility of engine harmonics loosening or actually breaking it. Kit includes all necessary spacers, pulley guides, and bolts to work effectively with most 3, 4, and 5 stage Dry Sump Pumps, alone or with belt driven fuel pumps. Pulleys sold separately.