Stars listed as standards of B9 Ia and A0 Ia spectral type. The differences between the two types are subtle. Only a moderate weakening of the He I lines with respect to the metallic spectrum. HD 21389 is the MK78 main standard and a Garrison (1994) anchor. By comparison, HD 223960 is earlier and notably more luminous. Although it is brighter than other Ia supergiants, it does not merit the hypergiant classification.