The Cobb Tuning Lightweight Crank Pulley is CAD designed and CNC machined from Billet 6061-T6 and anodized to withstand the toughest of under engine conditions. Replacing the factory main pulley, the lightweight unit improves acceleration by reducing the rotational mass of the stock unit by as much as 4lbs. Cobb's pulley is not underdriven and will not affect the life of your engine. The pulley is a redesigned, lighter rendering of the stock crank pulley. Installation is straight forward and can be done without jacking the vehicle or removing anything other than the belt cover, belts, and stock crank pulley.