Mass ratio distribution for BH-NS mergers in the low-redshift Universe (z < 1). For each BH-NS system, we calculated the mass ratio q = M_NS/M_BH ∈ [0, 1]. Values indicate merger rate densities estimated from the systems within each q bin, that is to say dRate dt⁻¹dV⁻¹dq⁻¹Δq, with Δq = 0.01. For transparency purposes, we use simple merger rate density as the vertical axis label. Most mergers have rather small mass ratios q ∼ 0.1 − 0.2, but there are also extreme mass ratio systems such as 56 M_⊙ BH + 1.3 M_⊙ NS (q = 0.023). For models with the delayed supernova engine (M280 and M283), there is a secondary peak for high mass ratios q > 0.4, which consists mostly of double compact objects with both components in the FMG (see Sect. 4).