Ceramicspeed titanium pulley wheelsupgrade your shimano rear derailleur with ceramicspeed titanium 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 titanium pulley wheels are extremely wear resistant and will outlive any pulley you have previously ridden ceramicspeed titanium pulley wheels are specially designed to reduce friction