Off all the bearings on a bike, the pulley wheels spins at the highest RPM. CeramicSpeed pulley wheels cut down on drag in your drivetrain compared to standard pulleys. The aluminum alloy is processed in Denmark and the Grade 3 ceramic bearing are installed at CeramicSpeed. CeramicSpeed has pulleys for Shimano and SRAM 9/10 speed road and mtb bikes and for Campagnolo 9/10 and 11 speed road. Feel the difference that high performance CeramicSpeed pulleys can do for your bike.