DuPont™ Styrofoam™ Brand Cavitymate™ Extruded Polystyrene Insulation is an XPS insulation board designed to fit between brick ties in cavity wall applications. 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.