SPEC billet aluminum flywheels are also CNC machined and exceed SFI standards for high stress racing applications. These units are recommended for highly modified street or racing vehicles, and for mildly modified street cars that can benefit from reduced rotating mass without the loss of daily drivability. The body of the flywheel is made of tempered aluminums, either 6061 T6 or 2024 T3, for ultimate strength and lightest possible weight. 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 or stainless steel rivets, depending on the application. These fasteners were chosen because of their exceptional strength and corrosion resistance. The ring gears are pressed on and secured with grade 10 fasteners. They gear is also heat treated for longevity. They are effective, durable and almost too pretty to install.!