The shade is good. It is suitable for eye-dropper demonstrator pens due to its washable property that does not stain the transparent plastics, resins, etc. of the pen like some other inks.

Very good ink, I have used it in various pens from Parker to cheap pens from eBay. Nice imprint on paper, in few cases you will find marks that have passed on the back (and I don't think the ink is responsible for those). Perhaps the only factor that I didn't give it five stars is that it gives the feeling that the color is not 100% consistent throughout the writing. However, the blue-black shade is unique in my opinion as it stands out from the majority of inks you will use in your notebook without drawing too much attention.

It is not a saturated black, it leans towards gray. Nor does the flow impress (the equivalent blue is very good and dark). The tests were done with a pen of the same brand. There is no other shade of black ink from the same manufacturer, while you have so many options from others...