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 F 876 and F 2262. 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 temperat