I've used zebra blue black inks in the past and found them to be exceptionally
good. The color was almost black with a hint of blue making them a unique
personal trade mark of sorts. These refills however were truly a
disappointment. The color was almost "turquoise" and the refills ink supply
runs out much quicker. Unfortunately, I was unable to return them within the
allotted time frame so am stuck with them.
This is absolutely the best pen I have found. The ink flow is smooth, not
scratchy. The ink dries quickly when put down on paper, so no smears. The blue
black color is excellent. Formal like black ink with a bit of flair. I even
use these refills in my Mont Blanc Generation rollerball pen.