They're insanely expensive / hard to find singly, so I just grabbed an
11mm obstruction box wrench and cut a small slit in the end with my
grinder.  You could buy a cheapo wrench at your FLAPS and do the same.
I used an obstruction wrench so it would be more useful in the annoying
tight spots on the brake system (union of the hose and caliper hard line
on each front wheel, etc.).

Best,
d.

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1990 GL -- Mudskipper