USG Sheetrock® Brand Glass-Mat Panels Mold Tough® are high-performance interior panels for new construction or renovation work. The panels have noncombustible moisture- and mold-resistant core encased in a moisture-resistant fiberglass mat that sheds water and features tapered long edges for easy finishing. The facer mat is colored to match traditional drywall and is engineered to accept the application of USG finishing systems. The back mat features USG’s distinctive green color.