I'm replacing the rear brake cylinder on my 2004 Hyundai Getz 1.3. Although the cylinder comes with the bleeder nut, it doesn't come with the union nut that is used to connect the brake hose to the cylinder. The hose is a standard 3/16" pipe.

I've had a look at my existing union (which I want to replace, but haven't got off yet) and it has 11mm flats. The bleeder nut that comes with the cylinder also has 11mm flats and the thread appears to be M10x1 as measured by a thread gauge.

I'm looking at the following part recommended by my local parts supplier:


The part is simply listed as "10mm". I'm not sure whether that refers to the distance across flats or to the thread diameter.

Another supplier has the following part:


These are just listed as "metric male".

When I've searched for flare nut wrenches, most of them don't seem to have an 11mm size, which is presumably what I would need to get these nuts off.

So I'm a bit confused regarding the proper sizes and specifications of these nuts. Can anyone clarify, please?

  • 1
    10mm refers to the wrench size needed m10 is the diameter of the male part of the fitting. I'd suggest instead of flaring if you don't already have the tools is to buy a premade section of line and install from the brake hose to the wheel cylinder.
    – Ben
    Jul 5, 2016 at 12:24

1 Answer 1


As it turns out, the part labelled "10mm" was the correct type. The flats are 11mm across and the thread is M10x1.

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