Thanks for linking this here. I'm one of the creators, and while I admittedly don't frequent this forum so I didn't want to just kickstarter post bomb, I'm happy to answer any questions I can.
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It's actually 2mm dense chipboard (think high end boardgame component stock) that's printed and die-cut. The final pieces have a lot of architectural reinforcement and double layering to make a very sturdy piece. We've got some examples on the PRODUCT QUALITY image in the kick info.