Physical parameters of the molecular shell of a GCIRS 7 and a sample of stars from the literature derived by single-shell and multiple-shell models by using interferometric and spectroscopic measurements. The contours shown correspond to 1 sigma from their respective hot solutions of GCIRS 7 obtained in this work, which are represented by the crosses with errorbars in blue and orange. The green, red, and purple symbols correspond to previous works for Antares, Betelgeuse, and μCep respectively (Table 3). The circles correspond to models where only visibilities were used, while the crosses represent models which use both visibilities and spectra. The dotted lines connect the inner and the outer layers on the multiple shell models in a same work.