Also called ‘commercial grade’, carbon steel is not stainless steel in that it instead features a carbon element of up to 2.1% in weight. The higher the carbon content, the stronger the bearing. With this, however, it becomes less ductile, has a lower melting point, and can’t operate large loads or high speeds. The benefits of using carbon steel bearings include being the cheapest bearing material for use as well as its hardness.http://www.awategroup.com/carbon-steel-bearing/