Hi Klaus,

IIRC my Square rigging is something like 4.5-5mm, and I thought it was Dux, but maybe I'm wrong there. In any case Erik Précourt built it. www.precourt.ca, see what he might have to say

edit: see below reference to Hampidjan's Dynex 75 which is in smaller diametres. You can compare it to the Dux, anyway. I guess my rigging is in this stuff.
http://hampidjan.is/media/pdf/Dynex_75_slittafla_april_2006.pdf

Edit #2: here's the page for Dux
http://hampidjan.is/media/pdf/002_Dynex_75Duxslittaflaagu02.pdf

In comparing the two, it appears that Dux is prestretched and Dynex 75 isn't?