Upper panel: B vs structure size for Set 2. The coloured area show the 1σ dispersion, and the orange dots a polynomial fit on the binned B vs size. Middle panel: ΔV vs size for the two categories of structures, with B larger than the orange curve in green, and with B smaller than the orange curve in magenta. Lower panel: Distribution of the perimeter/size ratio for these two categories of structures. The vertical black lines correspond to the typical granular size (dashed), the box size (solid), and the 20 ppm scale (network-active region interface, dotted).