From What i have seen rapid air has a economy line that is like regular pex and is straight plastic.
Rapid air also has a higher end that has the alumium in it.
There ia a line of pex that you can buy that has the aluminum in it as well. Most plumbers use this underground or in the slab.
If you use the alumium sleeved pex, you have to buy a little reemer that will remove the top layer of the pex to be able to band it correctly.
I will try to get some pictures of the tools needed to do the pex that I bought.
I purchased the tools to complete my house with and when I was getting ready to do my air in my shop I about fell over at the price of copper so I looked at other ways and came across the rapid air products and then started researching using pex.
Lots of people have used it and I think osha even permits it.
I tested mine to 175psi with no problems then I have a good regulator at my tank set to 125psi.
The one concern I had was would it stretch with pressure on it especially being in the top of my shop during the summer. It worked well all summer with very little stretch.
I've had PEX 3/4" in my shop for probably 10 years now. Very easy to install with brass fittings. I never turn the compressor off and it has never leaked. I run 130 psi all over the shop. You can get assorted fittings on Fleebay cheaper than big box stores. I bought the 20' sections of Pex=B from HD. Installation is fast and easy with the clinch rings. The tool for the clinch rings is not to expensive, and the cutter is the best way to cut it. You can get a set of cutter and clinch tool right now on Amazon for about $30.