This standard describes crosslinked polyethylene (PEX) pressure tubing made from material having a standard PEX material designation code of PEX 1306, or higher, according to ASTM* F876 and intended for use as underground potable water, reclaimed water, and wastewater service lines in sizes . in. (13 mm) through 3 in. (76 mm) that conform to a standard dimension ratio of SDR9. Tubing may incorporate an optional polymeric outer layer.