Pro X Steel Intake Valve Conversion Set Yamaha Yz450F / Wr450F / Yfz450 / Yfz450R / Gas Gas Ec450F The Steel Intake Valve & Spring Kits, developed by Pro X, provides a stronger alternative to OEM kits that typically use lightweight, yet less durable, Titanium valves. This kit introduces a set of steel intake valves and a set of stronger valve springs. The Pro X kit is compatible with OEM retainers, bases, and valve seals, and simply replaces the existing OEM valves and valve springs. 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