SHEETROCK Brand gypsum panels are factory-fabricated, composed of a fire-resistant gypsum core encased in heavy natural-finish face paper and strong liner paper on the back side. The face paper is folded around the long edges to reinforce and protect the core, and the ends are square-cut and finished smooth. Long edges of panels are tapered, allowing joints to be reinforced and concealed with a Sheetrock Joint treatment system. 12.7 mm and 15.9 mm Type C Gypsum Panels Specially formulated mineral core provides fire resistance superior to that offered by Firecode Core gypsum panels.