Total stellar mass and mass of the helium core (squares and circles respectively) of the 0.75 M_⊙ models at the arrival on the ZAHB as a function of ΔY_ini and for the different metallicities (colour-coded, see inset). For the highest [Fe/H] values (−1.15 and −0.5), the 1P models (i.e. ΔY_ini = 0) do not ignite central He burning and therefore do not appear on the plot. Full and open symbols correspond respectively to the models that do or do not reach the TP-AGB phase (and undergo at least two thermal pulses) after central helium burning