These ceramic bearing balls are great for applications were there will be extreme rotation and a premium performance bearing ball is required to meet the requirements.
Lighter and stronger than tungsten carbide, these silicon nitride balls are diamond polished, will not shatter or melt in the extreme conditions.
Higher hardness than chrome steel balls. Vickers hardness up to 1700HV.
the Si3N4 ball have G5 precision grade with tolerance 5/1000000.

Suitable for a range of purposes, some of the common are listed below:
-1/8" is often used for clusters and old English-style headsets
-1/4" is often used for rear wheels and bottom brackets
-3/16" is often used for front wheels