I started out by purchasing only 1 box - a pity it arrived with 2 of the cartridges already popped open, leaving a mess of blue ink on both ends of the box, inside the box, on the cartridges, etc. At first I wanted to "return it" but at these prices, never mind. One of the cartridges that popped open had 50% ink left in the barrel, and the other had about a third left.
The ink itself worked nicely. It has a beautiful tint, flows smoothly, and I can reuse the cartridges because some of the converters were "dubious" in quality.
For the future, I would suggest buying more of them, so that packed together they will be sturdier. Or buy the type of Pelican cartridge that comes in a tin box.