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Sheetrock ® Brand Gypsum Base Imperial ® , Firecode ® X (UL Type IP-X1) are 5/8 in. (15.9 mm) Type X gypsum panels that provide a rigid base for fire-rated veneer plaster systems. The panels feature a noncombustible gypsum core that is encased in a distinctive, 100% recycled blue face paper that controls water absorption, provides a strong plaster bond and resists plaster slide or slip under the trowel. The face paper is folded around the long edges to reinforce and protect the core, and the ends are cut square and even. The long edges of the panels are either tapered or square, allowing joints to be reinforced and concealed with Sheetrock ® Brand joint treatment systems. The panels are UL Classified for fire resistance and can be used in any UL Design in which Type IP-X1 panels are listed. On the face along the long edge of each panel, the UL Type Designation is printed for easy identification by building inspectors.inspectors.