These are by far some of the best gel ink refills I have ever used. The writing
is smooth up to .5mm but anything smaller and it does get a little scratchy...
It's just the nature of a roller ball being that small. One drawback, though,
is that the ink never seems to last very long. I go through a refill in about a
month. I don't know.. maybe it's because I enjoy writing with these so much!