Initial properties of progenitors of merging NSBHs. The blue, green, orange, and red dots represent binaries from channels Ia, Ib, IIa, and IIb, respectively. The left panel shows the primary masses versus initial binary orbital periods. The gray line indicates a 50 day orbital period for reference. The right panel displays the component masses with the gray lines indicating different mass ratios q, defined as M_2, i/M_1, i.