C4 cooler line fitting size
1/4" im pretty sure
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Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it
It's not NPT, it's a straight pitch with an o-ring seal( but I can't remamber the size right now, mabye it's 3/8-24 but not positive)..... I have seen people screw an 1/8" npt fitting into them though..... 
I always use the factory inverted flare adaptors with the o-ring and a 5/16 inverted flare to -6 and to adapt to braided line.....

I always use the factory inverted flare adaptors with the o-ring and a 5/16 inverted flare to -6 and to adapt to braided line.....
i just used 45* 1/4" NPT to -4 fittings. no leaks in over 2 years
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Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it
Ok, I was trying some 1/4" npt fittings but it only threaded in maybe a 1/4 thread before it got snug and I didn't want to torque on it if I had the wrong thread on there.
I have some 1/8" fittings and those are definately too small.
I have some 1/8" fittings and those are definately too small.
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