SPEC aluminum flywheels are CNC machined and exceed SFI standards for high stress racing applications. The SPEC lightweight flywheels are recommended for highly modified street or racing vehicles. The body of the flywheel is made of tempered aluminum, either 6061 T6 or 2024 T3, for ultimate strength and lightest possible weight or forged steel for maximum strength and durability. The 1/4 inch thick friction plate is a 1050 high carbon alloy, for incredible durability with any friction disc material, even iron. The plates are secured to the body by aerospace fasteners. The ring gears are pressed on and secured with grade 10 fasteners. The gears also heat treated for longevity.