I am a big fan of bottled inks, as the sagging shelf in my closet will tell you, but there is absolutely a case to be made for fountain pen ink cartridges. What you sacrifice in variety and cost, you make up for in convenience, and sometimes that is a price worth paying.
Sailor inks are some of my favorites, including the bottled blue black and both the black and blue black Nano inks in bottled and cartridge form. It was a foregone conclusion that I was going to try out the new Jentle ink cartridges, in blue black of course, and they work wonderfully.
All Sailor inks I have tried are well lubricated and flow smoothly in all nibs and in all nib sizes, and the blue black cartridge is no exception. I popped in into my medium nib Sailor Black Luster and it worked just as expected. The lines were solid and there were no flow issues at all. The only thing I noticed is that the color is slightly darker than the blue black ink from the bottle. This happens from time to time when comparing bottled inks versus the same ink in cartridge form. It's often not a dead-on match.
My only hope is that Sailor expands on this line to include even more colors. Pelikan has done this, adding matching cartridges to their Edelstein ink line, so hopefully this becomes a thing with brands. Yes, it is not as cost effective or environmentally friendly, but if the barrier to entry can be lowered even a tick I think it is worth it.
(JetPens is an advertiser on The Pen Addict and I received this product at no charge.)