Maximum spectral age estimates for the inner and outer doubles of J1021+1216, J1528+0544, and J2345–0449 (marked as stars) along with the linear sizes of the structures plotted on a logarithmic scale. The age uncertainties were omitted for clarity. The results from this paper are compared with DDRGs compiled in larger studies (Nandi et al. 2019; Marecki et al. 2021) and with a sample of GRGs (Jamrozy et al. 2008). The results for the inner doubles are marked in red.