Unions M10 X 1mm
I use "3/16 inch" copper because that's what my local factor has,i assume the metric is the same pipe re packaged for people born after 1970
IIRC my kit is DIN , my flare kit is not here to check because when I buy a car,one of the first jobs i do is check,clean,paint (or re-grease ) or replace any and all brake lines and hoses, I re-check pre MOT too ,but you need to match flares with what your joining to or is fitted .
What do you paint them with?
First jobs I do on buying a used car are remove all the wheels, discard any locking nuts, check for any play in steering joints, inspect tyres, inspect brakes, replace wheels, change oil and filter, check all lights, etc., washers, as for an MOT test. I shall henceforth do brake pipes next. Then change coolant, brake fluid, cam belt and pulleys.