Spec flywheels are CNC manufactured to an unprecedented .001 tolerance, in an industry where the standard is .010. This precision manufacturing process ensures perfect balance and a perfectly flat bed surface for the clutch disc, both of which also contribute to the ultimate in safety for competitive environments. All Spec flywheels carry SFI certification. The most responsible clutch component ensuring optimum performance and life is the inertia of the car. The flywheels contribution to power transfer has threefold. First, the inertia of the disc must provide a consistent and friction enhancing surface for the clutch. Flywheels also aid in proper operation, which is determined by the weight of the flywheel. Inertia controls the power to acceleration ratio and can make a weight faster or slower based on gear ratio, vehicle tire type, vehicle power output and even the location at which the output is achieved. The weight of a flywheel and the amount of inertia it provides can also effect handling. Finally, the flywheel must provide balance at rpm, meaning no damaging vibrations that rob the engine of power and dimensional deviation that produces smooth engine revs. To allow for that needs, Spec specific flywheels are manufactured from high grade carbon steel and aircraft grade aluminum. The Spec aluminum units are steel and mostly steel metal and feature a replaceable steel friction disc that is manufactured with a specially formulated friction-enhancing material for optimal clutch bedding and holding power. The choice of aluminum and steel materials provide a light to medium weight for all types of racing. Spec spends a lot of time and effort researching and developing flywheel weights and measurements optimal for all types of driving and racing and can optimize your MOI (moment of inertia) to maximize the output and performance of your car.