Kiel diagram for the components of the binary systems from Tkachenko et al. (2020) along with the stellar evolution tracks of models with masses from 5–20 M_⊙. For 5 and 20 M_⊙ the tracks with the maximum amount of IGW envelope mixing, log(D_env/cm² s⁻¹) = 5 and 6, are shown with the dashed-dotted and dashed lines, respectively. None of the models in this figure include the effects of rotational mixing. The binaries discussed in Section 3 are indicated by the black symbols (U Oph), red symbols (V1034 Sco), and blue symbols (V380 Cyg). The stellar parameters of the binaries are reported in Table 1.