American Gypsum's 1" M-Bloc Shaft Liner gypsum panels consist of a fire-resistant type X core that is encased in a mold and moisture resistant blue face and back paper manufactured from 100% recycled paper. The face paper is folded around the long edges to reinforce and protect the core. The panels feature a double beveled edge for ease of installation, with the ends being square-cut and finished smooth. M-Bloc Shaft Liner panels are available: 1" thick x 2' wide, and in a variety of lengths. At an independent laboratory accredited in accordance with ISO 17025-2005, M-Bloc panels have been tested to the industry s most rigorous standards achieving the best possible results per ASTM D3273, scoring a perfect 10 thus minimizing the risk of mold and mildew growth.