Stellar radius (R_⊙) versus T_eff for He-core WD sequences with different M_H. Shown are CE models at M = 0.3208 M_⊙ (M_H = 6.6 × 10⁻⁶, 10⁻⁶, and 10⁻⁷ M_⊙) and at M = 0.363 M_⊙ (M_H = 5 × 10⁻⁶ M_⊙) (Althaus et al. 2025), together with SRLOF tracks from Althaus et al. (2013) (blue dashed). The J2102–4145 components are shown with 1σ errors in R and T_eff, including the observed mass ranges of the primary (M₁) and secondary (M₂) (Antunes Amaral et al. 2024). The curve annotations in the plot indicate the stellar mass and H envelope mass, in the format M:M_H (both in M_⊙), for each evolutionary sequence. The primary matches an SRLOF model with M_H ∼ 3 × 10⁻⁴ M_⊙, while the secondary requires M_H ≲ 10⁻⁷ M_⊙ (see text).