Comparison of CO(J=2-1) with IRAS 60 μm for O-rich and C-rich AGB stars (left and right respectively). The colour and shape of the markers represent the stellar variability and chemistry type as in Fig. 4. Empty triangles are upper limits for the CO( J=2-1) intensities. Grey markers represent NESS sources. The solid black lines indicates the equality relationship between CO(J=2-1) intensity and IRAS 60 μm fluxes. The dashed lines represents linear fits to the points, solid and purple for our sample and NESS respectively.