Spectroscopic HR diagram showing the metallicity dependence of inflation for the analysed models in our grid. The left Y-axis shows the quantity log  (L/ L_⊙), whereas the right Y-axis shows the corresponding values of log  (Γ_e). The Γ_e values are computed assuming a solar hydrogen abundance (completely ionised). Models marked with open black dots are not inflated, whereas the coloured dots represent models with inflated envelopes. The colour of the dots indicates the strength of inflation, log  (Δr/r_core ). The black line is the ZAMS, and the masses of some representative models (in units of M_⊙) are indicated along it.