Just a little info.
Quills are used instead of dubbing for the body of dry flies. Sandfly's material is a bit different than a natural quill where it is already waterproofed. A quill will help make the segmented body look a bit more realistic, but natural quills can be a bit hard to work with so not all tyers like them. They don't necessarily match just the "red quill" or "black quill" hatches, but you can use them for any dry fly you like. I might jump on some of those too before the season starts up.
Ryan