Pro X pistons are precision machined on the latest, state of the art CNC equipment. The same low expansion, low friction piston alloy is used as is used for all major Japanese engine manufacturers. Pro X piston kits are a first class solution to replace your original pistons. Excellent economic alternative when you are looking for an O.E.M quality replacement piston Mainly manufactured in Japan by reputable Original Equipment Manufacturers to ProX exact specifications and high quality standards O.E.M.