Fractions of different types of post-MS companions of OB stars in our fiducial synthetic binary population relative to all post-MS companions, as a function of the mass of the OB star. For the companions, we distinguish core-helium burning stars (magenta), white dwarfs (blue), NSs (yellow), and BHs (grey). Shading identifies those companions that are paired with an OB star that rotates with more than 95% of its critical rotational velocities. The absolute number of binaries with post-MS companions expected in the SMC for each mass bin is given on top of the bin. The high-mass end (30–100 M_⊙) is presented with a wider bin width.