Left: region of the (T_eff, Δν) plane spanned by the reconstruction grid; the points mark the position of ZAMS (red), of the relative evolutionary age 0.8 (blue), and of the central hydrogen depletion (green). The black boxes show the typical extent of the 3σ regions in the initial and final stages of the stellar evolution. Middle: relative error on mass estimates with respect to the relative age of the stars. Only T_eff and Δν are employed for the estimate. Right: detail of the region around the M = 0.90 M_⊙ (black dot) for initial [Fe/H] = − 0.55. The red box shows the extent of 1σ region around the aforementioned model. The magenta diamond corresponds to the same model for initial [Fe/H] = − 0.50. The dashed line marks the evolutionary path of the model.