Since that is our axle I guess we would know best what it is, I know this b/c we are the only company in the country that A mass produces these, and B runs complete brake lines for the ease of the customer.
It is In fact copper- nickel tubing which is DOT approved. It has the benefits of being easy to work with, never rusts or corrodes. It is OEM on many luxury vehicles. Ford was going to swap to it last year but decided it was going to cost to much.
We spend more money to use this tubing as opposed to Standard steel tubing. We are a DOT approved brake line manufacturer though we may or may not have made those lines as Alliance also DOT approved was making them for us.
We have a significant amount of money invested in brake line equipment and assure all, we can make it out of whatever you want to DOT specs. All lines are also pressure tested to 3000 PSI which is close to triple what your brake system ever sees.
As for the axle being $1600 dollars, I do not know who the customer is so I don’t know the details but $1600 for a custom bolt in axle assemble with Braided stainless soft lines and copper nickel hard lines pre plumbed for you. That sounds like a great deal.
You may want to change your poll so we can Vote - OEM Copper nickel non rusting easy to work with tube. That would be my vote.