D4000_n and Hδ_A as a function of stellar mass for VIPERS stacked spectra of passive red galaxies. The linear fits to the whole VIPERS sample and to the SDSS sample are shown as brown dot-dashed and blue dashed lines, respectively. The slopes and relative uncertainties of the linear relationships between spectral features D4000_n and Hδ_A (S_D and S_H), respectively, and the stellar mass for the local SDSS sample and for the VIPERS sample are annotated.