RGBs in the HR diagram for models cgm1 to cgm5 of Table 4. The track of model mlt1 of Table 3 is also given for comparison. The solid line is model cgm1, the dashed line is model mlt1, the dot-dashed line is model cgm2, the three-dot-dashed line is model cgm3 and the long dashed line is model cgm4. The dotted line is model cgm5. The data are the six giants of group I defined in the text and Fig. 2. Following Fig. 4 the squares and triangles respectively stand for solar and subsolar metallicity objects. Only models cgm3 and cgm4 with lower α_cgm than the other models fit the data satisfactorily.