just be aware that you can get the same size line with all different thread sizes..
heres a example...all 1/4 tube ..different nuts..
https://www.summitracing.com/search?...%20flare%20nut
i used 3/16 and 1/4 in brake lines on my truck...and they all have the same size threaded inverted flare nuts...a good flaring tool is not a cheap investment,,but well worth the money...
i have the eastwood version...
i bought all my lines as premade 6ft lines from oreillys..and then cut to length and reflared