RK Racing Chain 520XSO-48 48-Links X-Ring Chain with Connecting Link 520XSO chains feature heat treated hi-carbon alloy steel components with seamless rollers and shouldered bushings, and are fitted with RK's proprietary RX-Ring seal design 520XSO chains offer quality, performance and unbeatable value, for all but the most demanding high performance application RX-ring technology offers less torsional friction, increased high-stress performance, and a 30% longer wear life compared to standard o-ring chains Viewed in cross-section, the X-ring has two lubrication pools and seal points versus the single seal point/pool design of a regular o-ring chain 520XSO has a maximum tensile strength rated at 8500 foot pounds and is suitable up to 750cc street bikes and 750cc off-road bikes