In most instances, Enduro Bearings uses 52100 High Carbon Chromium Alloy Races with heat treatment followed by cryogenic treatment. Starting with vacuum de-gassed chromium steel alloy, and hardened to Rockwell HRC 64, these super high precision races are cryogenically treated not once, but three times during the final super polishing phase as in Zero, CH or A/C bearings. Cryogenic treatment means taking the races down to minus 310º Fahrenheit (-190º C) to normalize the crystalline structure of the material so that the races will resist the hardness of the ceramic balls and get the maximum wear potential. This critical treatment to the races is left out by many manufacturers, but not by Enduro Bearings. For the top ZERØ bearings, we also additionally give them a Magnetite finish (black in color or Black Oxide) which is corrosion resistant and further stabilizes the bearing assembly. The races are again polished after this process to give the smoothest ball path.