The design process for this pulley ensured that a perfect factory replacement fitment was maintained while performance was maximized. It's a common misconception that the mass of a crank pulley alone determines its effectiveness. The truth is that it's actually the moment of inertia that affects the pulley's ability to improve engine and throttle response. The moment of inertia, in non-engineering terms, is a function of not only the mass of an object, but how that mass is distributed about it's rotational axis. A lower moment of inertia means that less torque is required to spin the crank pulley and, in turn, the crankshaft/engine. Our engineers took great care to keep the already minimal mass as close to the center of the pulley as possible without sacrificing its strength.