Variation of the convective core size at different stages during the core H-burning phase, as a function of the initial mass. The dashed lines are the models of Tkachenko et al. (2020) with strong convective boundary mixing, the solid ones are the present GENEC models with α = 0.2. The tracks in black correspond to the ZAMS stage, while the red tracks correspond to a stage where the mass fraction of hydrogen in the convective core (X_c) is 0.35, and the blue tracks to X_c = 0.1. The grey points show observed eclipsing binaries and their core mass estimates from Tkachenko et al. (2020). In the left panel, the GENEC models are the non-rotating ones. In the right panel, they are the υ/υ_crit = 0.4 rotating ones.