Comparison of measured δ⁹⁶Zr₉₄ excesses to AGB models. The four subgrains with anomalous δ⁹⁶Zr₉₄ are shown as open circles. Zirconium isotopic ratios in the envelopes of AGB stars 3−4 M_⊙ and low metallicity (Z = 0.0028 to 0.014) are plotted as colored lines, with markers indicating ratios in C-rich conditions in the envelope. Solar values of zero, by definition, are indicated with grey dashed lines. The uncertainties are 1σ.