Difference between the RVs measured from individual He lines and those measured from He iiλ4541 as a function of the spectral sub-type. The panel at the bottom right corner compares RVs obtained using all available He lines (except He i+iiλ4026 and He iiλ4686) with the He iiλ4541 RVs. The dashed line indicates the average of all comparisons weighted by their uncertainties. Only stars with constant RVs and data points with σ_ΔRV < 20 km s^-1 have been included.