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-50000-2 for: Polaris 250 TRAIL BOSS 1985-1999, 250 BIG BOSS 1989-1992, 250 TRAIL BLAZER 1990-2006, 250 XPLORER 2000-2002.