Final stellar mass (M_sc,final) obtained for IZw18 StSh models, as a function of the original cloud mass, M_gas,0. We plot with different symbols the three values of ϵ_ff for these calculations (as indicated by the inset legend). Each model colour shows the initial cloud radius, R_cl,0, as shown by the colour bar. Finally, the dashed lines present three different values (as shown in the figure) of the integrated star formation efficiency, i.e. ϵ_int = M_sc,final/M_gas,0.