Yes, it's the bubble wrap, they sell rolls of 2 inch tape bubble for spacers. I don't use pre-fab though all of my duct is custom made per job, and when I make
my order I can choose how I want it wrapped. I do occasionally take wrap jobs though and the bubble is super easy to work with.
Gas line is pro-press g and super nice to work with. Inspector loved it. Just has to be marked.