The supposed standards, but if you've ever dealt with the international mind, standards are...uh...flexible


...US...UK.......Italian
mm...inches.mminchesmminches
4..3.3.0.13..2.8.0.113.1..0.122
5..3.0.0.12..2.67...0.1052.9..0.1142
6..2.8.0.11..2.54...0.102.7..0.1063
7..2.54..0.10..2.4.0.095.2.5.. 0.0984
8..2.3.0.09..2.29...0.092.3.. 0.0906


1 mm = .0394