My boss loves the Keurig, so we have a couple machines here at work, and way too much horrible coffee in k-cups, so I just popped one open.
The grind for this Green Mountain Sumatran is pretty much as Joshua suggests, much finer than typical pre-ground drip coffee, but not quite close to espresso. Gritty fine sand.
I'm happy to open another brand if you like. Oh, wait, out of curiosity I opened a Tully's house blend and it's pretty much the same grind.
And John, you know you'll have to get one of the refillable k-cups if he doesn't have one, right?
"A screaming comes across the sky..." - Thomas Pynchon