Can't recall for sure, but I believe copper lines are not DOT legal in the US. As mentioned, the good alternative is Cunifer, a copper nickel steel alloy, hence CuNiFer.

I have stainless steel lines on my MGB, the flares are unforgiving and difficult to seal against the brass unions. I bought them pre-bent, took about 15 minutes to install the set. They shipped in a HUGE mostly empty cardboard box - it weighed more than the lines did, lol.

My Spitfire got a set of Automec copper-alloy lines, as I think Cunifer is a trademark, but they look identical.

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12 E70 3.5i xDrive
03 E46 330i ZHP
01 E53 3.0i
98 E36 323is
12 Audi A4 Quattro
79 Triumph Spitfire
73 MGB