The advantage as I see it is access to a very wide assortment of colors in a very wide assortment of wire diameters. The wire is coated, which seals in the color and prevents tarnishing. For those who would like to try colored copper wire in something beyond the standard copper, gold, red, black, green and chartreuse offered at some fly shops.
You might find a few other colors here Wes...;^)
<http://www.linesend.com/product/thread_etc.shtml#ultra>
They are coated as well.
...byard --
Byard Miller Line's End Inc <http://www.linesend.com> Virtual Flybox <http://www.virtualflybox.com>
