Precision balls can be supplied in different materials. Depending on the application, there is a choice of aluminium oxide, zirconium oxide or silicon nitride. The ball dimensions and the level of finish are specified in the ISO 3970 standard. In addition, it is possible to machine the balls to conform to your specific application.
The rings in the picture are made of Yttrium stabilized zirconium oxide. This provides thermal and electrical insulation, combined with mechanical properties that are better/comparable to those of steel. An additional advantage of this material is its extremely fine grain size. This makes the material ideally suited for high-precision components.