From the Manufacturer
Unique Ander-Lign compression fitting is the only fitting that is completely assembled with a captive sleeve. This fitting also comes with a brass insert. The bodies are interchangeable with standard compression fittings for additional ease of use. For use with copper, brass, aluminum, thermoplastic and plastic tubing (when used with Watts insert part#967-P). It is not recommended for use with steel tubing. Lead-free brass is not more than a weighted average of 0.25% lead when used with respect to the wetted surfaces of pipes and pipe and plumbing fittings and fixtures. This compression fitting is easy to use for both contractors and the do-it-yourselfer. Not for underground use.