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Sheetrock Brand UltraLight Panels Firecode X (UL Type ULIX) are the industrys first and lightest Type X gypsum panel. These lightweight panels have been formulated to achieve all the strength and performance characteristics as standard 15.9 mm (5/8 in.) Sheetrock Brand Firecode Type X Gypsum Panels at a significantly reduced weight. The panels are cUL Classified for fire resistance and can be used in the most widely specified UL fire-resistance-rated wall, column, floor-ceiling and roof-ceiling assemblies where Type X or Type C panels are required. The long edges of the panels are tapered, allowing joints to be reinforced and concealed with Sheetrock Brand joint treatment systems. On the face along the long edge of each panel, the UL Type Designation is printed for easy identification by building inspectors.