A closed-cell high-density polyurethane, which is another way of saying it's awesome!
The material makes GenStone lightweight and easy to install without making a mess.
Each panel is cast from four unique molds made from real stone or brick, in order to avoid repetition and make the stones look more realistic. They are also hand-painted, so they all look unique and more real.
If a fire is a concern, you can also special order Class A fire rated panels to help protect your building.