Complete kit of 16x Valve springs, Retainers and Spring seats for Nissan 200SX S14 / S14A / S15. SUPERTECH uses their experience of more than 20 years in the manufacturing of racing valve springs retainers & valvetrain components, along with the application of computerized Finite Element Analysis (FEA). They perform intensive testing and work closely with many engine builders in order to continuously improve and provide the market with the best possible product for every application. SUPERTECH valve springs are made with premium Superclean Chrome Silicon Vanadium Steel alloy for higher performance & durability at high RPMs and better memory. They are computer designed to ensure that wire stress levels do not overpass the limits of stress defined in the diagrams of fatigue for long durability under extreme conditions. Proprietary computer programs aid in maintaining harmonic control. Retainers are manufactured with high quality military certified Titanium alloy, CNC machined for a tight fit that will ensure long durability. SUPERTECH also manufactures quality high-performance valve guides, cam followers, keepers & spring seats. SUPERTECH VALVE SPRINGS feature: Finite Element Analysis (FEA) design Superclean Chrome Silicon Vanadium Steel alloyHigher than stock seat & open pressures for high-lift, long duration cams.