what sort of material are they made of? it looks amazing, the way they shimmer in the sunlight is very cool.
Its chikara silver - an aluminium coated Spinnaker Nylon.
If you like it at this lighting conditions you should see that with the sunset reflections - it looks like this:

Yeppers this is very much like the Elliot Speedwind BUT LARGER >>>>>>>>>>>>>>>
The video shows normaly Speedwings with an 82,5 cm landing edge, its the stack of a friend. Shape and bridle builded by the
Handkerchief plan with my sail design.
This Pic shows the relations - left speewing 82,5 cm, right 1 Meter (thats mine)

The 1 meter speedwings, as an 8 or 9 stack, are monsterkites with an explosive pull. You have always to be focused on them. Every wind gust can drag you down.