Final CO core masses of BH progenitors and their corresponding BH formation masses for the components (both primary and secondary) of detectable merging BH-BH systems in four of our models: M30, M50, M60, and M70 (see Table 2 for an overview of all the model ingredients). For readability, the filled areas encapsulate 96% of all the BHs, excluding few outliers and showcasing the M_CO to M_BH relation for the representative majority. The presented models are different in ways that affect the BH formation masses, that is, the PPSN/PSN prescription (see Sect. 2.3) as well as the assumed fraction of mass lost in neutrinos during a BH formation (1% in M30, M50, M70, and 10% in M60). We note that model M70 only differs from M30 and M50 for M_CO ≳ 32.4 M_⊙, whereas model M50 only differs from M30 for M_CO >  37.5 M_⊙. Those threshold core masses correspond to the threshold helium core masses M_He in different models PPSN/PSN prescriptions.