Yep - A4 is another one of those International 'ISO' standards sent to test
the patience of the the good 'ole US!!

Just out of interest - when something like the space station is built - is
it put together with metric or imperial/us screws/bolts?  Given US dominance
of the project I'd asume non metric - Imagine though the fun & games as
Sergi, the russian cosmonaut, askes if he can borrow Sams 5/16" wrench as
his 14mm don't quite fit - I think not!!

STeve