Namura uses the best materials matching the ring design to its application. Often overlooked and unglamorous, they are an essential part of an engine's efficiency and durability. The materials used in the manufacturing of piston rings are one of the most critical factors in their performance. Meets or exceeds OEM specification, only use with Namura Pistons. Fits Namura Pistons: NA-10003 for: Honda XR400R 1996-2004, TRX400EX 1999-08, TRX400X 2009-14.