Profiles of the abundances (in mass fraction) of H, ³He, of the carbon isotopic ratio, and of the thermohaline diffusion coefficient at various evolution points on the RGB (see Fig. 1): slightly above the bump (point B_1.25, black solid line), at the luminosity of the contact (point C_1.25, red dashed line), close from the RGB tip (point D_1.25, magenta long dashed line), and at the RGB tip (point E_1.25, blue dot-dashed line). The abscissa is the scaled mass coordinate δM that allows a blow up of the region of interest (δM = 0 at the base of the HBS and δM = 1 at the base of the convective envelope).