Valve inlet (steel) + springs sets Prox    Alternative where OEM titanium valves are used as titanium valves require a very precise installation procedure. OE titanium valves are also of poor quality, while high-end titanium valves are very expensive. Thus, titanium valves must be replaced frequently and cause correspondingly high costs. The Prox kits contain special, stronger springs. The kits thus replaced the OEM valves and springs, where, for example, the OEM brackets, valve seats, etc. can be reused. The steel valves offer increased durability and have a 3 times longer service life than the OEM titanium valves. Due to the additional weight of the steel, the reinforced springs must be used! - Steel valves with increased service life and less wear under extreme conditions - Nitrided valves provide high microhardness, while the super smooth surface reduces friction between the shaft and guide - Springs are made of high quality chrome vanadium steel for higher performance and durability at high speeds - No modifications to the engine necessary as OEM brackets, seals, etc. can be reused