For joining Pex-Al-Pex pipe on to any fitting with an existing compression nut and olive (e.g. radiator valves).
Use pipe reaming tool to bevel the end of the Pex-Al-Pex pipe.
Remove nut and olive from existing fitting and place MTA olive and nut on over the Pex-Al-Pex pipe.
Slide together and tighten accordingly with suitable wrench.