These aluminum flywheels are made from the highest quality 6061 t6 aluminum, fantastic for strength, heat dissipation and of course reduction in weight. for the friction surface they use 1045 steel and attach a replaceable friction surface with military grade aerospace fasteners. with these replaceable friction plates there is no need to replace the entire flywheel when the clutch or flywheel is at the end of it s life, saving time and money. the ring gears are made from 1050 steel and are heat treated for durability. the flywheel ring gears are heated then pressed on and secured with grade 8 button screws. fidanza flywheels are engineered to perform.