Same as Fig. 5 but for [Rb/⟨Sr+Zr⟩] vs. [Fe/H]. Blue dots are M dwarfs in this study. Grey dots corresponds to the giants and dwarfs stars analysed in common by Gratton & Sneden (1994), Tomkin & Lambert (1999), and Mishenina et al. (2019). Red open circles are stars in which Rb lines may be affected by the magnetic field. Coloured solid lines are the GCE predictions as in Fig. 5. The black solid line shows the GCE prediction when the weak s-process is inhibited in massive stars (i.e. no rotation).