Ceramic ball especially Si3N4 have the following performance as low density, high strength, low friction coefficient, electrical and magnetism resistance, wear resistance, well rigidity, lubrication and maintenance free when working, it's the best choice for rollers (inner ring and outer ring are made by metal) of the hybrid construction which are used in high-speed, high accuracy and long life environments. Normally, GCr15 or (AISI440C,316 304) makes inner ring and outer ring; The ceramic ball can adopt ZrO2, Si3N4 or Sic. 

If you interested in ceramic bearings, please feel free to contact me at Fiona@xlb.cc

More information please browse website http://www.bj-xlbearings.com/ceramic_bearings.htm