The PERRIN Performance? lightened crank pulley for the Scion xA & xB is engineered to reduce rotating mass, increasing horsepower and torque. Made from 6061T6 aluminum and weighing in at 1.3lbs, the PERRIN? pulley is more then 4 lbs lighter then the stock crank pulley. The PERRIN? pulley is not under driven and will not affect the life of your engine. The pulley is a redesigned, lighter rendering of the stock crank pulley. Aftermarket, under driven, pulleys are prone to charging and drivability problems from being excessively under driven. The PERRIN Performance? lightened crank pulley will have no effect on your cars charging system. The PERRIN Performance? pulley achieves power and performance by reducing the rotating mass of the crank assembly. That reduction is effectively the same as removing 100 pounds of weight from your vehicle. The PERRIN Performance? pulley will not wear out engine bearings or the oil pump, and will not add any additional vibration or noise. This is the newly designed Perrin Pulley for the Scion xB/xA