This Aerospace Recommenced Practice (ARP) defines a series of ball bearings which are specifically designed to support the rotor in a dynamic balancing machine. By establishing certain bearing sizes the number of required balancing machine support adapters will be reduced. The intent is that each size bearing identified by its outside diameter and width will be capable of accommodating any bore diameter within the specified range of that size. This ARP specifies both the nominal dimensions and the tolerances for a series of ball bearings with semifinished inside diameters which are suitable for supporting gas turbine rotating components in dynamic balancing machines.