Figure shows that the same position in the HR diagram can be reached by stars of different masses if the α parameter is changed. This effect is shown with respect to a 0.8 M_⊙ star model with α = 1.9 (solid line) by comparison with models with α = 1.68 and masses in the range 0.8−0.95 M_⊙ (dashed lines). The boundary conditions are the same as our reference set of models.