Density distributions as functions of interior mass for the whole star (panel a)) and the inner region of 8 M_⊙ (panel c)) and as functions of radius for the whole star (panel b)) and the inner region of 1 R_⊙ (panel d)) in pre-SN models B15 (blue line), N20 (green line), W18 (magenta line), and W20 (red line). The central collapsing cores are omitted. For a comparison, the black line shows the structure of a nonevolutionary pre-SN model used by Utrobin (2005).