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 1This specification covers the requirements for materials, workmanship, dimensions, performance, and markings for metal insert fittings with o-ring seals and copper crimp rings for use with SDR9 cross-linked polyethylene and SDR9 cross-linked polyethyle