CeramicSpeed Shimano 11-Speed Pulley Wheels - Coated Bearings, Silver - Pulley wheels that reduce friction, last 3-5 time longer than stock high-end pulleys, and reduce overall drag within the drivetrain. Grade 3 Silicon Nitride ballsHand built in DenmarkCoated races increase bearing service life by increasing hardness of race and reducing corrosionThese pulleys are compatible with all Shimano 11-speed rear derailleurs that aren't XT or XTRCeramicSpeed products with coated bearings include a 6-year warranty