Ceramic ball bearings have greater hardness than steel ball bearings which result in longer ball life. Ceramic balls have a smoother surface finish than steel balls which means less friction when your wheel is spinning and this translates into increased performance. Ceramic bearings require less lubrication and exhibit less lubrication degeneration, whichresults in increased bearing life. Our fully sealed ceramic cartridge bearings are ABEC-5 and use Silicon Nitride (Si3N4) ceramic balls with 440C stainless steel races. The ceramic bearings produce an unparalleled ride in terms of smoothness, quickness and efffortlessrolling. All magnesium wheelsets contain ceramic bearings. ceramic bearings canbe installed in new wheelsets or ordered as kits. The road ceramic kits contains 2 x 688 and a x 6803C3 ceramic bearings. The MTB ceramic bearing kit contains 6 x 6803C3 ceramic bearings. Look for the yellow seals signifying American Classic's top quality ceramic bearings