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