Surface helium enhancement of 5 M_⊙ SMC stellar models as a function of stellar age. The y-axis shows the increase of the surface helium abundance of the stellar models with respect to their initial abundance. Here X_He and X_He, 0 are the current surface helium abundance and the initial surface helium abundance of the stellar models, respectively. The orange solid line corresponds to our nonrotating MESA models, while the solid, dashed, and dotted blue lines correspond to our MESA models, the SYCLIST models, and the MIST models that initially rotate at 40% of their critical velocities.