The little filament really is very comfortable and painless in almost all of my insertions. My left arm tends to feel it very slightly more than my right, but usually only for 30minutes or so.
The filament feels springy but flexible, kind of like a tiny bit of carbon fibre (very much like my carbon fibre bagpipe drone reeds if that’s any help - probably not😛).
The needle is probably as thick as the Medtronic Quickset insertion needles, but I generally feel it less than cannula insertions.
I met a little girl (7yo) with a Libre while I was traveling in South Africa last week, she barely felt hers at all, and was busily flinging herself off a mechanical bull at the time.
