This Auction is for (1) LEIGHTWEIGHT ALUMINIUM, RACING, CRANKSHAFT PULLEY to suit BMW 2002 - E30, or any BMW/M10 engined vehicle. At high revs this 348gr. (OE pulley 488gr.), 75mm., Billet Aluminum crank pulley slows down the alternator and water pump by 40%, which frees up horse power and allows water pump to opperate at opimum speed for water circulation and cooling. This pulley features a steel surface on which the front engine seal runs. Contact seller for more details and information if needed.