Unusual Trailer

Spotted this rig while passing through Greytown today. I originally noticed the raised rear axle on the trailer, but once I stopped to look I realized that the trailer was made entirely of aluminium.

As far as I am aware Manac trailers ,as this is branded, are only made in Canada and the US, so it's surprising to see one in NZ. It must be considerably lighter than a steel equivalent, but I would have thought considerably more expensive as well.
The truck is a 2007 Scania P420.