Two identical standard international piston converters, 0.75 ml, brass piston nut, steel mixing ball. There is no difference from the single except the price per unit and the fact that having two solves the actual problem, which is that changing ink means emptying a converter that still has 0.4 ml of a perfectly good colour in it.
With two, you fill the second, swap it, and put the first in a small bag until the colour comes round again. A capped converter holds ink for weeks without drying. This is how most people who use several inks actually work, and nobody tells you to do it.
Same fit and same care as the single: everything here except the Quire Pocket Pen, wash before first use, a trace of silicone grease on the seal every year or two. Supplied in a card sleeve rather than two blisters.
