We've used those things before. They are OK for someone who has difficulty tying a fly on the river or someone who can't see well enough at dusk to tie a different fly on. We used them for sub surface, I think they are to much weight for drys. My wife used them so she could change flies on a evening fishery so as not to bother me. They make it quick to change flies. As for sticking in the end of a hollow fly line, not quite sure where that came from. We used them on the end of our tippets. You can buy different sizes from very small to seeable. Try one you might like it. Just your personal preference. We still carry some with us.

fish