Godspeed Project custom springs are made from SAE9254 steel wire and cold wound. These springs provide perfect solution for tuners looking to swap to a different spring rate setting due to driving situation and car setup. Godspeed Project custom springs are available in 8, 10, 12, 14 and 16 kilogram per millimeter(please see chart for specs.) With 62 mm I.D.(86 mm O.D.) will allow these springs to fit most coilovers within dimension range in the market today.