Review on Uxcell Carbon Bearing Precision 600Pcs by Adam Walsh

These are ordinary steel balls, not precision bearing balls. They have an average diameter of 0.1774 inches (4.506 mm) with a standard deviation of 0.0002 inches and a maximum diameter variation of 0.0011 inches for ten samples. In comparison, "normal" bearing balls made of chrome steel have a dimensional tolerance of +/- 0.0001" (max. spread 0.0002") or +/- 0.0025 mm. They are not hardened and can be scratched with an x-acto blade (hard stainless steel).