American Gypsum 1/2-in x 4-ft x 8-ft Mold Resistant Moisture Resistant Regular Drywall PanelM BLOC gypsum panels were developed as an improved mold and moisture resistant wallboard with a fire resistant core encased in a mold and moisture resistant blue face paper and brown back paper manufactured from 100% recycled paper. At an independent laboratory accredited in accordance with ISO 17025 2005, M BLOC panels have been tested to the industrys most rigorous standard achieving the best possible results per ASTM D 3273 scoring a perfect 10,