The ALTA LCP is engineered to increase horsepower and torque. The 0% Stock Sized pulley is a lighter rendering of the stock crank pulley which will not wear out engine bearings or the oil pump, and will not add any additional vibration or noise. The 2% Over-sized has all the same features of the 0% Stock Sized pulley but adds more boost to your car (on Supercharged Cooper S models only). By simply increasing the diameter of the pulley boost is increased, safely and reliably. Unlike some aftermarket pulleys which are underdriven and prone to charging and drivability problems, the ALTA Performance lightened crank pulley will have no effect on your cars charging system.