Mass-loss rates vs. wind velocities for DARWIN models of carbon stars at different metallicities (solar, LMC, and SMC) and the corresponding observed properties for Galactic carbon stars and four sources from the LMC, derived from CO-lines (Schöier & Olofsson 2001; Ramstedt & Olofsson 2014; Groenewegen et al. 2016). All panels show the same data but with color-coding according to stellar luminosity (upper left panel), effective temperature (upper right panel), carbon excess (lower left panel), and piston velocity (lower right panel).