Chemical composition as a function of the interior mass coordinate of a non-rotating model with M_ZAMS = 25 M_⊙ and [Fe/H] = −2 at the pre-SN stage. We show the chemical composition up to the mass coordinate of 15 M_⊙. We report the abundances of H (black line), He (red line), ¹²C (green line), ¹⁶O (blue line), ²⁰Ne (magenta line), ²⁸Si (orange line), ⁵²Cr (dark red line) and ⁵⁶Fe (gray line).