Throughout the world, carbon dioxide cylinder valves have a special thread. In Europe, Africa and much of Australasia, the thread conforms to British Standard 341 Part 1 (.860 in x 1/14 in W) or the direct European equivalent (DIN 477, SN 219505, etc). These threads are in effect interchangeable.
British BS341 No. 8 European DIN 477 No. 6 and SN 219505 Type 7
French NF E 29-650 Type C Australian AS2473 Type 30
America CGA 320 and Japanese JIS B 8246 CO2 threads are different and are not compatible with each other nor with British/European CO2 threads).
http://www.teamonslaught.fsnet.co.uk/gas%20thread.gif