1.1 ,This specification covers metal insert fittings with o-ring seals and copper crimp rings for use with Cross-linked Polyethylene (PEX) and Cross-linked Polyethylene/Aluminum/Cross-linked Polyethylene (PEX-AL-PEX) tubing in ¹/₂ ,, ³/_4, ,1, and 1¹/₄ ,in. nominal diameters that meet the requirements for Specifications F876 or F3253, and F2262 respectively. These fittings are intended for use in 125 psi (861.9 kPa) (PEX-AL-PEX) and 100 psi (689.5 kPa) (PEX) cold- and hot-water distribution systems operating at temperatures up to and including 180 ,°,F (82 ,°,C). Included are the requirements for materials, workmanship, dimensions, performance, and markings to be used on the fittings and rings.