[Fe/H] versus radius of RGB stars inside model sex156, a Sextans-type dSph with a perigalacticon of 63 kpc and an apogalacticon of 150 kpc (model sex156). The colour from light yellow to dark red shows the relative number of points within each [Fe/H]-R bin, normalized to the highest density within each individual model. The thin dashed (blue) line shows the mean metallicity (⟨[Fe/H]⟩) within each radial 200 pc bin from the centre, the thick dashed (black) line shows the median metallicity within each bin while the solid (red) line shows the least-squares linear regression of the metallicity versus radius (at the distance of Sextans, 1 kpc = 40′).