BH mass from the scaling method (using saturation of the photon index with the mass accretion rate), M_scal, compared to the corresponding dynamical masses M_dyn for stellar mass BHs. Data are taken from ST09, Shrader & Titarchuk (2003), Shaposhnikov & Titarchuk (2007), Seifina & Titarchuk (2010; for M_scal values), and Greene et al. (2001), Hjellming & Rupen (1995), Herrero (1995), Ninkov et al. (1987), Munoz-Darias et al. (2008), Hynes et al. (2004), Park et al. (2004), Orosz et al. (2002), Sanchez-Fernandez et al. (1999), Sobczak et al. (1999), Petri (2008), Homan et al. (2006), Filippenko & Chornock (2001), Miller-Jones et al. (2021; for M_dyn values). The yellow strip indicates a BH mass spread of 1.3 M_⊙. The deviation from the yellow strip for Cyg X–1 reflects new estimates of the BH mass (marked with an pink arrow), taking into account the strong wind in this binary and possibly associated with the refinement of the source distance (from 2.5 to 2.2 kpc) from the radio data – due to which the BH mass estimate increased in Cyg X–1 from 6.8–13.3 M_⊙ to 21 M_⊙ (Miller-Jones et al. 2021).