Final mass of helium in the envelope, as calculated by Eq. (10), shown in solid lines as a function of the initial mass of helium stars of different metallicities. The final total mass of the helium-rich envelope is shown in dashed lines for comparison. The dots on each line indicate, for each metallicity, the initial helium star mass at which the transition between WN- and WC-type mass loss is observed to occur in the models. The rhombi indicate the value of the minimum initial mass above which helium stars are observable as WN-type stars, obtained via Eq. (8). Helium stars below this limit do not have optically thick WR winds and have overestimated mass-loss rates.