Micro-turbulent velocity of the sample stars separated by spectral luminosity (Gr.1–4), and by SpT and LC (same symbols and colours as in Fig. 3 with SPBs highlighted by a blue five-pointed star). Overplotted in gray are the adopted v sin i (same symbols as in Fig. 8). In each panel the horizontal solid and dashed lines indicate, respectively, the mean value of the upper detectability limit to v sin i averaged “by eye”, and the corresponding ${\overline{v}}_{\text{mic}}$ (for more information see text).