Ratio of the average abundances of different chemical species in the ejecta of AGB stars with an initial mass 1.5  M_⊙ (top panel), 4  M_⊙ (middle panel), and 6  M_⊙ (bottom panel) and the initial mass fractions. The different lines refer to the Z = 3 × 10⁻⁵ (black) and Z = 3 × 10⁻⁷ (green) model stars we investigated and to the Z = 3 × 10⁻⁴ (red) models published in D19. Dotted (dashed) lines in the panels refer to the results of Z = 3 × 10⁻⁵ models obtained by assuming an overshoot parameter a factor 2 lower (higher) than in the standard case. Long-dashed and dot-dashed lines in the middle panel indicate the results of the evolution of a 4  M_⊙ model star with Z = 3 × 10⁻⁵, obtained by modelling mass loss according to Blöcker (1995) by assuming a value of the free parameter of η_R = 0.005 and η_R = 0.02, respectively.