... ) ID 25, OD 47, W 12MM3) Material: ZRO2,white color, SI3N4, black color , SIC black color4) Shield/closure: Open, ZZ, 2RS5) Tolerance: ABEC ... , Si3N4 stands for the silicon nitride ceramic material and is black colored, 3.Ceramic ball Bearings, SiC stands for the silicon ... dioxide, also known as zirconia or zirconium oxide, they are white colored, a ZrO2 ball looks exactly like a pearl. 5 ...