... :ZZ. 4,Noise level:Z1,Z2. 5,C2,C0,C3. high Performance ceramic ball bearing-china bearingWe have 2 types of ... . and the ZrO2 that stands for the zirconium dioxide, also known as zirconia or zirconium oxide, they are white colored, a ZrO2 ... heat generated.full ceramic Si3N4 ZrO2 Full Complement Thrusthybrid bearings high Performance ceramic ball bearings-china bearing