Mass loss rate versus wind velocity for M-type AGB stars: black symbols (stars) mark observations by Olofsson et al. (2002) and González Delgado et al. (2003), red symbols models of series A and blue symbols models of series B (triangles and squares indicate pulsation amplitudes of 3 and 4 km s^-1, respectively; see Table 1 for details). We note that the stellar parameters of the models where chosen to produce weak to moderate winds, as such environments seem to be favorable for Al₂O₃ formation.