I've had no technical difficulties with any of these refills so far. The nibs
aren't too dry, but they are stiffer than I originally thought, so the range on
line width is not all that great. But I personally enjoy super fine lines, so
that works out perfectly for me.
The color is a soft bluish grey, and I found it to be dark enough to read.
Perhaps it's a hit or miss kind of thing, but I ordered five different colors
and have had great results with all of them so..
I specifically use these pens for my planner, as it has thin paper, and the thin
lines produced by these do not bleed through in the least. But I've also done
some fairly broad strokes using the side of the nib, and bleed-through was
minimal on even my cheapest copier paper.
Pros: Nice fine line, lovely bluish dove grey ink. "Extra Fine" really is EF. I
imagine it works great for writing characters with many detailed strokes.
Cons: These pens (well, refills, but I use them just as pens) tend to get blobs
of ink on the tip while capped, no matter how they're stored. On some papers,
they take an extremely long time to dry completely. I seem to be using up the
ink very quickly, sketching rather than writing.
YMMV: The pen holders look weird with the refill sticking out the back. I'm not
sure whether the blobbing problem has to do with something like the
heat/pressure from using the refills without a holder. If I were more motivated
to test them, I'd experiment, but I don't care for the holders and I like a
narrow pen, and this is working well enough.
Overall: I love this soft grey for sketching and for fine, small writing, and it
hasn't blobbed yet. It's functional enough to get a middle-of-the-road, 3-star