Fitzpatrick & Massa (2009) NIR extinction parameter α_NIR as a function of R_V (large black squares), see Eq. (1). The fit parameters for our model as a function of E_g (α) are shown by the coloured squares (crosses), the colour-coding as per Fig. 7. The thick squares use the model R_V and the thin squares the best fit R_V values from Eq. (1), shown as the dashed lines in Fig. 9. The vertical grey band shows the typical diffuse ISM value of R_V.