Blue O-Ring 100L Chain & Silver Sprocket 15/38 for 2004-2007 Yamaha YFZ450 450 15 Tooth Front Sprocket, 38 Tooth Rear Sprocket and 520-100L Blue O-Ring Chain All Race-Driven sprockets meet or exceed OEM specifications and use hardened S45C steel. O-Ring Chain helps keep the pins lubricated which reduces friction and helps the chain last longer. Fits 2004 2005 2006 2007 Yamaha YFZ450