Mass ratio q vs. BH mass M_BH for NS–BH mergers in our metal-poor (green circles) and metal-rich (purple circles) models, compared to the measured values for GW190814 and GW190426_152155 (white stars). We include the combined distribution for metal-poor (red squares) and metal-rich (yellow squares) binaries derived from Giacobbo & Mapelli (2018) (model CC15α5). The black boxes enclosing GW190814 and GW190426_152155 represent regions deviating <30% from the observed M_BH and q. In the side histograms, the dotted lines identify the measured mass and mass ratio for both GW sources, while the shaded (empty) areas encompass the measured 90% credible level for GW190814 (GW190426_152155).