ProX piston rings are made by original equipment manufacturers to exact specifications. ProX uses well known brands like Rikken Japan, TP and NPR to ensure and get the highest quality possible. All ProX piston rings can be used in cast iron, nickel ceramic coated (Nikasil), boron composite and electrofusion cylinders. If the application has an OEM cylinder with chrome bores, ProX supplies a different piston ring as in the ProX piston kit.