different brake line materials what do you use?

I don’t know either. Someone else was talking about this stuff a year ago and no one could offer up any engineering info. But I bought some for my truck I was working on at the time. As far as I’m concerned it’s junk. As you said too soft and pinched way too easy. Had to go to 3 parts stores to get all I needed in steel. They said this is going to be the new stuff. Ya cheaper for them.