I didn't see this listed so:
https://www.kickstarter.com/projects/archonstudio/dungeonsandlasers-plastic-tabletop-rpg-scenery
I received an engineering sample of the product today. They're made of hard gray injection-molded plastic, my guess would be ABS from its hardness and density. The floor and wall ties fit together tightly, though it takes a bit of effort that likely would wear at paint on those surfaces had they been painted. Due to response from earlier sample recipients, the production tiles will be slightly larger than the samples.