Primary vs. secondary BH masses for BBHs that merge in a Hubble time. The contour plot shows the mergers for binaries with M_BH, 1 ≥ 20 M_⊙, while the distributions show the full mass range of primary and secondary BH masses on the top and right. The solid blue, dashed green, and dash-dotted pink lines refer to simulations with stellar tracks computed with the Ṁ_rdw, Ṁ_Γe, and Ṁ_L/M rates, respectively.