radio-controlled planes, model trains and R/C cars).
It's much
easier to find the metric ones here (England) than the imperial
sizes.
The good (and thus expensice) toolshops I freqeunt seem to stock both
ranges. Darn it, they ecen stock thost crazy US sizes, like 11/32"
combination spanners (needed to take the PSU out of an HP9810/9820, BTW)
-tony