...the big one and the width of the small ones.
The dimples on the circle part of the roof also look more defined, though I can't tell if that's a structural difference, or just a difference in the lighting.
I've really got to get rid of my desire to see clean-sheet designs.
One question, why do nearly all of the UG structures have the "button" on top of the cylindrical components?
And no offense, but it kind of looks like it has weeds growing on top of it.