Various Galactic metallicity models to investigate the potential role of bi-stability braking, with initial masses between 20 to 60 M_⊙, and initial rotational velocities ≈300 km s^-1. For reference, the Geneva models (red, E12) and the Bonn models (green B11) are indicated. (Note that there is no 30 M_⊙ but a 32 M_⊙ model available from the Ekström et al. (2012) grid.) For the set-up of MESA models MB1 to MB4, see Table 6 and Sect. 5.7.