4x8 , 2 inch thick, Foamular 250 XPS Boards are a closed cell rigid spray foam board with an R value of 10. Easy to install continuously, underground, or on concrete walls. 2 inch XPS board meets code requirements for continuous insulation and also for moisture barrier requirements. Rated for 250 PSI, so perfect for below slab applications of subfloor insulation. 40 sheet available and will offer discount for complete purchase. Home Depot sells the 150 PSI sheets (interior) for $37 per sheet.