After I Buy LEGO Education Large Building Plates 4570274 (4 Pieces)I remember having a big gray plate like the 15x15 in this set, when I was a kid, some 35+ years ago. It provided a great base for building and being able to move your model w/o it crumbling to pieces. And that still holds true.
However, the plate seems a bit flimsier than I remember. Admittedly, time has a way of distorting memory. But I have some reservations about moving heavier models mounted to the bigger plate, due to it's flexibility. It should work fine on a firm surface, but could prove frustrating on a rug or softer surface.
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