Properties of the evolutionary models of stripped stars (see Table 1) shown as function of metallicity. The markers and connecting lines highlight when the central helium abundance is X_He,c = 0.5, these values are given in Table 1. The shaded areas indicate how each model evolves from core helium mass fraction of 0.9 to 0.05 during core helium burning. We highlight the model with metallicity Z = 0.0166 with a black plus sign (described in Sect. 3).