The ProX steel valves are manufactured of premium grade steel to exact OEM specifications and tolerances. the steel valves are made by the leading OEM factories in Japan and are a direct and cost-efficient OEM replacement.; ProX Racing Parts headquarters are located near Amsterdam, The Netherlands. Founded in 1975, ProX Racing Parts is now distributed in a significant number of countries worldwide. Domestic as well as international dealers and distributors are being served from our facilities in Nieuw Vennep Netherlands, Mentor Ohio, and Woodstock Ontario Canada.