as I did replace ALL brake lines I used Werkstoff: CuNi10Fe1Mn
90 % Kupfer und 10 % Nickel, Ø 4,75 x 0,78 mm (hope the dia measures are correct - if needed I go in the basement for a doubble check), called CuNIFer (smile)
Is "supposed" to be approved and I had no issue on the picky German TÜV.
Advantage as above is easier to work with, used a simple tool/"plier" to bend it and a simple tool to "fix" the ends (if foto need I go in basement). At the rear neer the gear box the circle is very small so needed some tricks to do it..using a tube of adeq. diameter and slowly and slowly bendt it. .. and got it tight after def 3 attempts.
also as the material is a bit softer it is easier to make the connection tight..which is not easy..see picture above with the "fitting" looking pretty much used. You need the very correct tool to tighten it think is 11, 12 13 mm..!! There are tools with a small opening to fit the tube more like a ring tool. I use those. Works also nice on the clutch line I had more problems which is ORIGINAL Cupper, but make it tight took me a while altough less pressue (TX Jack, did not know that, although expectable).
Well as also above you might move to int. versions per adpter..which I do not like on Brakes as any more links increase the risk of failure.
Matthias /Böblingen Germany