Pro X Steel Exhaust Valve Conversion Set Kawasaki Kx450F / Kfx450R The Steel Exhaust Valve & Spring Kit from Pro X is designed as a stronger option for the less durable titanium valves often found in OEM applications. This kit features a set of steel exhaust valves in combination with more robust valve springs. The advantage of this kit is its compatibility with the original equipment there's no need for additional purchases as it can be installed with the OEM retainers, bases, and valve seals. Features: Steel Valves for increased durability and less wear under extreme conditions Chrome vanadium steel valve springs deal with the extra weight of the steel valves Fully rebuildable with OEM retainers, bases and seals without the need of any further engine modifications Nitrided valves offer high microhardness while super-smooth surface finish reduces friction between stem and guide