Left panels: comparison between spectroscopically inferred values of T_eff (top), R (middle), and ﹩\mathrm{log}(g)﹩ (bottom), based on Sonora Diamondback atmospheric models, with those derived from evolution models. Benchmarks younger and older than 300 Myr are shown in blue and orange, respectively. Linear fits to the atmospheric–evolution parameter relationships are overlaid, including a single fit of the full sample for T_eff and separate fits for R of the young and old subsets. Right panels: differences between atmospheric- and evolution-based parameters are shown as a function of spectral type. Open diamonds indicate the mean and rms of the parameter differences within individual spectral type bins from M8 to L6, as summarized in Table 4.