Comparison of the R₁ and R₂ ratios for different grids of tracks in the top and bottom panels, respectively. All the values are computed from tracks with Z = 0.002. Continuous lines indicate tracks presented in this work. The FMRS tracks have a standard He (Y = 0.249) and [α/Fe] = +0.3. Tracks FMRS+He are computed with Y = 0.4. Dashed lines show models from Lagarde et al. (2012) with (Lagarde rot.) and without rotation (Lagarde). All these tracks have Y = 0.25 and [α/Fe] = 0. Dotted lines show the MIST models from Choi et al. (2016), with (MIST rot.) and without rotation (MIST). The models are computed with Y = 0.252 and [α/Fe] = 0