Evolution of surface boron abundances as a function of surface gravity for 15 M_⊙ models computed within the purely diffusive scheme with the MESA code. The solid blue and dashed red lines indicate models with only transport by meridional currents and by the secular shear instability computed with and without magnetic fields, respectively. The dotted orange line indicates a non-magnetic model computed with the impact of the dynamical shear, the Solberg-Høiland and GSF instabilities in addition to the meridional circulation and secular shear instability. Within this purely diffusive scheme, the predicted surface boron abundances are found to be nearly insensitive to the different instabilities considered (in particular regarding the inclusion of magnetic effects) provided that the meridional circulation is accounted for.