Evolution of the total mass of ¹²C (top), ¹⁶O (middle), ²⁰Ne (bottom) for a single (blue) and a binary-stripped star model (red) with the same reference core mass of 6.3 M_⊙. The evolution is shown from the moment of core helium depletion as a function of the time until core oxygen depletion. The curve marked by inverted triangles (i.e., the lower boundary of the colored bands in each plot) indicates the total mass of each isotope inside the helium-depleted core. The upper boundary marked by circles shows the total mass of this isotope in the star. The red and blue shaded regions thus highlight the mass of this isotope in the shell above the core.