The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
>>It's not for tying flies if that's what you're thinking. It's for cross stitching.>>
I have no idea what it is, but if you Google it, you'll find that it is indeed used for fly tying.
This is the way it often goes and the reason you'll often find tiers prowling the aisles in craft and hobby stores like Michael's, etc. waiting to be struck by a lightning bolt of inspiration.
Other than what we can imagine and then make happen, there really is no limit to what we can decide to call "fly tying materials".
It's part of what makes it fun.
Where are they available in the US?