2pcs. 3x8x4mm Precision Ball Bearings Hybrid Ceramic Metal Shield Chrome Steel 52100 (GCr15) Precision Races, Ceramic Si3N4 Balls Compared with steel, ceramic materials are noted for their better or particular characters, such as wear-resistance, corrosion resistance, high temperature resistance, electrical insulation (except SiC), non-magnetic, high strength, high rigidity, and low specific gravity. These properties qualify them for replacing steel to make bearings serve in conditions of higher speed, harsh environment and less lube. Decrease wear, noise, vibration and maintenance time of bearings, and eventually increase performance, reliability and life of bearings.