The material of the roll ball: Silicon Nitride Ceramic(Si3N4)and Zirconium Oxide Ceramic (ZrO2) The material of the inner and outer ferrule: The Steel ,the stainless steel Use characteristic: High Velocity, High Precision, Low Noise, Long life and so on Apply domain: Machine tool, Computer, Medical Equipment, Sport Equipment Etc. We can satisfy the customer?s request to manufacture the bearings.