Radius of each of our single stellar evolution models at the time when they begin burning helium in their cores. At Z = 0.014 (red), higher-mass stars expand to radii ≳10³ R_⊙ prior to core helium burning. At lower metallicities, however, higher-mass stars expand late and have radii almost an order of magnitude smaller at this time. They will therefore struggle to create long-lived stripped stars.