I'm on my computer at work right now so I can't crack it open to tell you (unless you're considering an old original Rage). But I do know that the Voodoo3 2K is substantially smaller than the old Voodoo2s. Just as a referenence I THINK that it's the exact same dimensions as a Monster MX300 since I have them mounted directly next to each other. That probably doesn't help you much, but it's better than nothing. I would think it would fit in most places.
Make it idiot proof and someone will make a better idiot