Top left panel: SED of the blazar S5 0014+813 along with a KERRBB model (blue line). The model has ν_p ≈ 15.33 and . The SS mass is Log M_SS = 9.96; the KERRBB mass limits, corresponding to a = −1 and a = 0.9999, are Log M_Kerr = 9.59 − 10.16. In the SED fitting process we did not account for the data point at Log ν ~ 15.4, probably contaminated by the Lyman α line. Top right panel: SED of the blazar SDSS J013127.34-032100.1 along with a KERRBB model (blue line). The solid blue line has ν_p ≈ 15.21 and . The relative SS mass is Log M_SS = 9.91; the KERRBB mass limits, corresponding to a = −1 and a = 0.9999 are Log M_Kerr = 9.54 − 10.11. The solid black line is the continuum extrapolated from Yi et al. (2014). Bottom left panel: SED of the blazar SDSS J074625.87+254902.1 along with a KERRBB model (blue line). The model has ν_p ≈ 15.38 and . The SS mass is Log M_SS = 9.07; the KERRBB mass limits, corresponding to a = −1 and a = 0.9999, are Log M_Kerr = 8.70 − 9.26. The solid black line is the continuum extrapolated from the SDSS catalog. Bottom right panel: SED of the blazar SDSS J161341.06+341247.8 along with a KERRBB model (blue line). The model has ν_p ≈ 15.22 and . The SS mass is Log M_SS = 9.45; the KERRBB mass limits, corresponding to a = −1 and a = 0.9999, are Log M_Kerr = 9.08 − 9.65. The solid black line is the continuum extrapolated from the SDSS catalog. In all panels, the orange vertical line highlights the Lyman α line position; we did not consider the frequencies higher than this line for our fit. The IR data (Log ν < 14.5) are probably related to the emission of a dusty torus and/or a nonthermal emission (i.e., synchrotron) and we did not account for them for the fit.