Convective regions during the evolution of an 1D 25 M_⊙ star model simulated with the MESA code. Shaded regions correspond to convection zones. The color-shading represents the mixing-length theory (MLT)-predicted Mach number. The black solid line denotes the total mass of the model. The red vertical line indicates the point in the evolution at which the SLH simulations start and the mass extent of the initial model. The green lines indicate the mass entrainment at the upper and lower boundaries as extracted from the 3D hydrodynamic simulations. See discussion in Sect. 5.4.