JT Sprockets JTSK9011 525X1R Chain and 17-Tooth/41-Tooth Sprocket Kit Fits: BMW F650 GS (8.5mm bolts) 08-12 Kit Contains: 17 tooth Chromoly Front Sprocket; 41 tooth Steel Rear Sprocket; & JT 525X1R-116 Link Chain SCM415 chromoly steel alloy is used for the front sprocket, and ultra-durable high carbon C49 steel for the rear sprocket JT X1R Heavy Duty Chains are constructed with quad riveted pins for an extra strong rivet that resists powerful lateral forces on the outer plate X-Ring seals are used for a better seal and produce less friction than conventional O-ring chains