Mass–radius exponent (blue) of our initial 60 M_⊙ model evolved to a central helium abundance of 0.8, and a H/He gradient of that is then exposed to a constant mass-loss rate of 10⁻⁵ M_⊙ yr⁻¹ as a function of the remaining stellar mass. The green line gives the surface helium abundance. Because mixing is inhibited during the mass-loss phase, the surface helium-abundance evolution reflects the internal helium profile of the initial model.