RK Racing Chain 4067-039S Steel Rear Sprocket and 520XSO Chain 520 Steel Conversion Kit Fits: Yamaha YZF-R6/YZF-R6S 03-05/06-09 520 steel conversion kit contains: 15 tooth chromoly front sprocket; 48 tooth steel rear sprocket; and RK 520XSO-116 link chain RK's new XSO chains offer quality, performance and unbeatable value, for all but the most demanding high performance application Viewed in cross-section, the RK 'RX-ring' has two lubrication pools and seal points versus the single seal point/pool design of a regular O-ring chain All components of the MXZ4 chain are heat treated using RK's exclusive HIT (Heat Induction Transfer) process and include a clip type master link