Binning in intrinsic colour-magnitude space used by APOGEE (left) and APOGEE-2 (right) to select their Main Red Star Sample targets from the 2MASS catalogue. The exact magnitude limits between the three cohorts (short, medium, and long) depend on the field and are provided by the APOGEE collaboration in auxiliary files. The selection is computed as the ratio of successfully observed targets to available sources in each of the three (in APOGEE) or six (in APOGEE-2) regions.