DuPont™ Styrofoam™ Brand Cavitymate™ Ultra ST-100 (SB) XPS Insulation is a moisture-resistant, durable and lightweight extruded polystyrene foam board specifically designed for use in wet cavity wall environments. Manufactured with a patented carbon black technology, Styrofoam™ Brand Cavitymate™ Ultra ST-100 (SB) features an R-value of 5.6 per inch (RSI of 0.97 per 25 mm). Its closed cell structure provides advanced long-term thermal performance and moisture control.