Washer size for motherboard standoffs?

mace200200

Honorable
What size washers do i need? I'm thinking about buying a Fractal Design Define XL R2 case. One of the big complaints with this case is I guess sometimes they ship with standoffs that are to short? So when I order it I figure I'll want some washers just in case but don't know what the inside diameter needs to be and don't have a caliper anymore that I could measure the threads with. Even if I don't need the washers this wouldn't be a bad thing to know anyway.
 
Solution
Most motherboard standoffs accept a 6-32 thread size. The finer thread screws in most computer assembly kits are M3 metric screws.

6-32 hole ~3mm, and an outside diameter of ~5.5mm or 7/32 of an inch.

mace200200

Honorable
Did some more research, I was actually wrong about the conductivity of the washers. It seems that boards these days use the case as a ground so I guess you actually need to use conductive washers. I read that people on these forums have used metal washers before with other cases when they're GPU's and pci cards won't seat all the way.