Hi,
There was at least 3 in-line design changes on the ARX, one change was that the leading edge got narrower and the kites turned faster. Then there was the material changes relating to the mylar problem. The latest one does not have the mylar lamination on the outside at all and some even came with Polyfuse that was developed for the Aero.
Throughout last year you can also find small changes in the velcro attachment for the valve caps etc.
Thanks,
Bengan
http://www.colonawatersports.com