1.1 ,This specification covers crosslinked polyethylene (PEX) push-fit mechanical fittings for use with crosslinked polyethylene (PEX) tubing in ¹/₂ ,, ³/₄ ,, 1 and 1 ¹/₄ , in. nominal diameters that meet the requirements of Specification F876. These fittings are intended for use in residential and commercial, hot and cold, potable water distribution systems as well as hydronic heating, including under-floor heating systems, up to and including 100 psig (6.90 bar) and 180°,F (82°,C). Included are the requirements for materials, workmanship, dimensions, performance, and markings to be used on the fittings.