Ceramicspeed pulley wheelsupgrade your rear derailleur with ceramicspeed pulley wheels for reduced friction and extended lifetime. The pulley wheels are the fastest spinning bearings on your bike, making an upgrade to ceramicspeed an effective way to save you precious energy. Ceramicspeed aluminium alloy pulley wheels are specially designed to reduce friction to an absolute minimum, virtually eliminating the drag associated with standard pulley wheels. The special design helps guide the chain in its ideal line and perform super smooth shifting.features ceramic bearings longevity, 3 5 times longer than steel bearingsmaintenanceit's important that you properly lubricate your bearings in order to ensure optimal performance and maximum longevity. Add oil to the outside of the bearing seal, so that oil can penetrate the bearing. Do this when you lubricate your chain, or if you have washed your bike or have been riding in wet or muddy conditions. Buy ceramicspeed components from chain reaction cycles, the world's largest online bike store.