Sprockets synchronization improved shifting precision, less stress for the chain Ultra-Shift teeth shape provides upshift optimizationOptimized teeth space for longer life, lower wearNickel-chrome surface treatments on steel for longer life, lower wearLight-alloy lockring for weight savings12,13,14,15,16,17,19,21,23,25,27236 gramsCS9-CH127Velo Mine Customer Service 217.679.2356217.679.2356 or 217.827.1173217.827.1173