¹⁸⁶W/¹⁸⁴W vs ¹⁸³W/¹⁸⁴W from single large grains (LU) and the average of small grains (KJB, dark grey circles with 1σ error bars from Ávila et al. 2012) compared to the surface evolution of Set 1 and Set 2 stellar models of solar (top panel) and of double-solar metallicity (bottom panel) of different masses (see legend). Circles (Set 0) and triangles (Set 2) on the lines represent the composition after each TDU after the envelope becomes C-rich. The dashed black lines represent the solar composition (δ = 0 by definition). The solid black line is the regression line from Ávila et al. (2012).