Yellow Non O-Ring Chain & Silver Sprocket 15/40 100L 2004-2008 Yamaha YFZ450 15 Tooth Front Sprocket, 40 Tooth Rear Sprocket and 520-100L Yellow Non-O-Ring Chain All Race-Driven sprockets meet or exceed OEM specifications and use hardened S45C steel. Non-O-Ring chain doesn't have o-rings between the links so it is lighter, thinner and has less drag. Fits 2004 2005 2006 2007 2008 Yamaha YFZ450