Sorry, I think this may have been answered before, indirectly, but I just want to ask it directly. I have a 2009 I'm replacing the front rotors, calipers, etc. Metal brake line needs replacing, started leaking at the joint to soft line. Everything on this truck so far has been metric, and when I took the fitting to the parts store it screwed into the 10mm hole. I am trying to splice the line and put in a new flare end. I've bought the adapter, but a 3/16" compression sleeve will not fit on line, and 1/4 is way too big. I think the line *must* be 6mm (which would go along with the 10mm male connector). But everything I read says it is standard 3/16". Please Help! LOL

 

I believe it is 6mm.

I even double-checked, and VatoZone and AdvincibleAuto has them in 6mm that says it's application fits on a 2009 F150.

Here's VatoZone: https://www.autozone.com/brakes-and-..._0_90073_92949

Good luck...........