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1/4 in. (6.4 mm) Sheetrock ® Brand Gypsum Panels feature a noncombustible gypsum core that is encased in 100% recycled face and back papers that form a high strength composite design. 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 tapered,allowing joints to be reinforced and concealed with Sheetrock ® Brand joint treatment systems. 1/4 in. (6.4 mm) panels are recommended as an additional layer for improving sound control in double-layer wood- or steel-framed partitions, and as a face layer for use over old wall and ceiling surfaces. These panels comply with ASTM C1396, Standard Specification for Gypsum Board and are UL Classified as to surface-burning characteristics and noncombustibility and have achieved GREENGUARD Gold Certification qualifying low VOC emitting material (meets CA 01350)