Styrofoam™ Brand Wallmate™ XPS Extruded Polystyrene Insulation is a moisture-resistant, durable and lightweight rigid foam board that can be installed directly onto interior masonry walls. It features a slotted edge and is designed to accommodate a wood nailing strip between the insulation boards for quick and easy installation. The Styrofoam™ Brand XPS product line gives you the proven thermal and moisture performance of the original XPS, plus the product options you need to design and build energy-efficient, resilient structures all the way to the top. It’s lightweight and easy to install, which makes the work go faster, and it’s readily available through our wide distributor network. When and where you need it, Styrofoam™ Brand is there.