Spectroscopic HR diagram showing the boundaries (dotted lines) between non-inflated and inflated models for different metallicities such that below a given line, we do not find any inflated model for that metallicity. The solid lines represent the ZAMS. The masses at ZAMS for some of the models have been indicated. The right Y-axis represents the logarithm of the classical Eddington factor considering X = 0.73, similar to Figs. 3 and 5. The horizontal line marks the location Γ_e = 1 and the hatched region above it is the forbidden zone where no hydrostatic model can lie.