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Sheetrock ® Brand UltraLight Panels Firecode ® X (UL Type ULIXTM) 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.