Description Loose Needle Roller Bearings: High Quality Graded Hardened Chrome Steel roller made from Chromium AISI 52100 steel. Hardened to 60-67 Rockwell Scale equivalent to 700-900 HV (Vickers Scale) and are hardened all the way through the roller. These are the same hardened steel rollers used to manufacture needle roller bearing assemblies and have a high duty and life cycle. These hardened rollers are highly suited as replacements for bearing components, drive transmission parts, pivots, shafts etc. Benefits: Hardened and ground, precision components, AISI 51200 chrome steel, 60-67 Rockwell hardness Brand / Quality: Simply Ital Ball - High Quality Outside Diameter: 4mm Length: 4mm Technical