Bolt size

[OGCollard]

So i am trying to get my brake bleeder screws loose after redoing my brakes and needing to bleed them problem is they are pretty darn snug. Been hitting them with som pep spray to help. I have been trying to find the correct size wrench for them. The 10 mm, and 3/8 are snug but not exact. Anyone know the correct size for this nut?

[4.3LXJ]

Seems to me that I used 5/16" IIRC

[OGCollard]

5/16 sounded possible. Nope. 5/16 too small, 3/8 too big, and if i trcall from last night 10mm was a tad big too. Any other suggestions?

[4.3LXJ]

8 or 9 mm

[OGCollard]

A 6 pt 3/8 deep well socket does it. But have to do it carefully as it wants to rock a little