Gravitational NS mass M_NS, grav and BH mass M_BH, grav as a function of the initial mass M_ini of stars (panel a) and the CO core mass M_CO (panel b). The large grey boxes indicate models with potential (here unaccounted for) fallback that may result in weak or failed SNe. The light yellow triangles are for models that have reached their maximum radius before core helium burning and thus cannot undergo Case C mass transfer. They are shown here mainly for completeness.