Ferrea Single Valve Spring - 17-21 Honda Civic Type-R K20C1 - Set of 16 (Req Roller Rockers) - S10166Harmonics or high frequency fatigue is present in all racing engines and will usually destroy the valvetrain if not controlled. Properly designed valve springs will control the dominant harmonics, provide the needed stability, and reduce valvetrain component wear. Ferrea valve springs are developed from high strength alloys, including premium grade chrome silicon steel. Our springs are heat treated and stress relieved, which dramatically increases the