Percentage (in grey scale given in the legend) of case Br mergers as a function of initial (ZAMS) primary mass and binary mass ratio for different combinations of β and η or α. On top of each figure we also give the overall case Br merger frequency. O+S means that the matter leaving the binary takes with the specific orbital and spin angular momentum of the gainer. If the mass leaves the binary taking with it only the specific orbital angular momentum (label O) of the gainer, there are no mergers. The percentages are calculated assuming a flat orbital period distribution. As outlined in the text, this implies that ~48% of the massive binaries are case Br.