Top panel: BH mass as a function of the BH spin computed using the KERRBB and SLIMBH models (solid and dashed lines, respectively) for a fixed spectrum peak position and different viewing angles (0°, 30°, 45°) for the source J1342. The yellow area represents the virial mass range (Log ) estimated by BN18 using the MgII line. Central panel: same comparison for the source J1120. The light yellow shaded area represents the virial mass range (Log ) estimated by MR11 using the MgII line; the dark yellow area is the virial mass range (Log ) estimated by De Rosa et al. (2007) using the same procedure. Bottom panel: same comparison for J0038. The yellow shaded area is the virial mass (Log ) estimated by W18 using the MgII line. Orange dots represent the BH mass solutions coming from the classical SS model: these correspond to particular KERRBB/SLIMBH solutions with a precise spin value. The confidence interval (±0.1 dex) is derived assuming a small uncertainty on the spectrum peak position on which the BH mass estimates are based.