The CON-40 is often disparaged for its meager ink capacity and inability to (easily) get a full fill, especially in comparison to its much larger cousin, the pump-action CON-70. That said, I agree with Monika's review that this converter is ideal for swapping out inks frequently either if you are trying to find a new favorite, or simply get tired of colors quickly (as I do). The metal agitator beads do a good job of breaking the surface tension of the ink, providing a pretty consistent flow. It also cleans out easier than any converter I've ever used, with only a few backfills necessary to get all the ink out of the chamber. The CON-70, by comparison, can be a nightmare to get completely clean. If you always use the same ink, or otherwise need the high capacity, then the CON-70 is probably better for you (as long as your pen fits it), but otherwise this little guy does the job just fine. My only gripe is that it's very lightweight. Not a huge deal for metal pens, but resin pens like my Custom 742 felt a lot more substantial in hand when fitted with the heavier CON-70. The lower maintenance of this converter still makes it worth it though.