Paul,
I purchased the ones I have tied some flies with. I think the package actually said "fly lips" or something similar.
They are tough to adjust, and twist when you cast or strip 'em too fast even after getting the fly to swim right.
But... they can be fished downstream by feeding and holding. They are killer for dropping back into a deep river bend under the branches. The fly will wobble like a lipped balsa wood plug on the hold, then dead drift back at depth when you feed. The word "Sexy" does not do them justice.
It is a deadly technique... almost too productive... and kinda like Euro-nymphing... is it flyfishing?
To me, it's a last resort kinda thing. But there are a few in my flybox.
Gary