Filled symbols: average critical velocities V_c and the related dispersions against the MK spectral type for luminosity classes V, IV, and III. These V_c were calculated using the effective temperatures and bolometric luminosities from calibrations carried out by various authors. Open symbols: critical velocities for the average MK spectral types and luminosity classes that conform with the method used in this work to obtain the V_c for individual stars. The MK spectral types are represented with the BCD parameter S₇₀ dex.