This 12-sided polygon consists of 7pcs. of PC-3a and 6pcs. of PC-4a modules, all connected with 20pcs. of Ø25mm standard PVC pipes (used in the electric community in Denmark). The length of the pipes will determine the size of the polygon.
The polygon is tested with 100mm long pipes and is very rigid :-)
The two corner modules are both part of my free 'He-Ideas' building kit.