Circular orbital velocity and mass ratio $\stackrel{\sim }{q}=m_2/(m_1+m_2)$ for binaries containing a CO and post-MS high-mass companion in the fiducial model. On the left, we differentiate between systems where the post-merger remnant is the CO (pink), and where the post-merger remnant is the stellar companion (blue). The dashed black curves indicate lines of constant accretion efficiency proxy $\eta \propto {\stackrel{\sim }{q}}^2/v_{\mathrm{circ}}^4$, with labelled values showing the fraction of systems above each line where the CO is the post-merger remnant. We distinguish the systems with a NS companion (triangles) and a BH companion (squares).