Comparison of the two black hole accretion models employed in the StarTrack code. We present the evolution of the mass transfer rate from a donor star (Ṁ_don; top panel, solid lines), BH mass accumulation rate (Ṁ_BH; top panel, dashed lines), BH mass (M_BH; middle panel), and BH spin (a_spin; bottom panel) during the RLOF stable mass transfer phases. Critical mass transfer rates (above which mass ejection from a system is expected) are provided for reference. During the first part of the RLOF (t ≈ 4−4.8 Myr) the donor is a MS star, during the short-duration peak it is a HG star (t ≈ 4.9 Myr), and for the remaining RLOF it is a helium-core burning star. See Sect. 2.4 for a description of the full evolutionary path and both accretion models.