USG Sheetrock® Brand Mold Tough® Panels are available in Firecode® X and Firecode® C formulations. Both panels feature a noncombustible, moisture-resistant gypsum core that is encased in moisture- and mold-resistant, 100% recycled green face and brown back papers. The panels also feature tapered long edges for easy finishing. USG Sheetrock® Brand Mold Tough® Panels Firecode® X (UL Type SCX): Available in 5/8" thickness and UL Classified for fire resistance. USG Sheetrock® Brand Mold Tough® Panels Firecode® C (UL Type C): Available in 1/2" and 5/8" thicknesses and UL Classified for fire resistance, these panels feature a specially formulated mineral core that provides fire resistance superior to that offered by 5/8" USG Sheetrock® Brand Mold Tough® Panels Firecode® X.