FWHM_min versus the initial Lorentz factor Γ₀ for a number of Type-II GRBs. Left: the values for the latter were taken from different data sets, which are colour-coded: L12 (Lü et al. 2012), X19 (Xue et al. 2019), Y17 (Yi et al. 2017), X16 (Xin et al. 2016), and X20 (Xie et al. 2020). Dashed lines correspond to the typical distance at which the dissipation process responsible for the prompt emission could take place. Right: same as left, except that we calculated Γ₀ from the data set by Ghirlanda et al. (2018). Red points are the GRBs belonging to their golden and silver samples, while blue points are lower limits on Γ₀.