16mm conduit is available in Australia but you rarely see it used. With the limited application where you could use it for the only slight savings in cost it's not worth the trouble of carrying it around with all it's associated fittings. For the same reason I often use 6mm² where 4mm² would be allowed. You have to weigh up what's worth stocking so you can get by in a van rather than having to drive around in a pantech.
