1.1 ,This specification covers outside diameter controlled, black metric-sized and IPS-sized crosslinked polyethylene (PEX) pipe, fittings and joints, made in pipe dimension ratios ranging from 6 to 17, and pressure rated for gas distribution. Included are requirements and test methods for material, workmanship, dimensions, burst pressure, hydrostatic sustained pressure, stabilizer functionality, bent-pipe hydrostatic pressure, degree of crosslinking, chemical resistance, and squeeze-off. Requirements for pipe and fittings markings are also given. The pipe, fittings and joints covered by this specification are intended for buried gas distribution and gas transmission pressure piping applications.