1999-2008 Honda TRX 400 EX (11:1 Hi-Compression) ATV Engine Piston Ring Kit [Bore Size (mm): 86.47] Bore Size (mm): 86.47 Ring Kits Include Piston Rings Only - Piston Not Included Namura Piston Rings Fit Both Namura and OEM Pistons of the Same Bore Size Unless Otherwise Specified Compatibility: 1999-2008 Honda TRX 400 EX (11:1 Hi-Compression)