A: The jars don’t really do it for me, although I do have one in one of my humidors, and it does help contribute a little more moist air to the system. For the most part, they tend to take up valuable real estate. I much prefer the crystal-filled humidifiers that form a gel-like substance when charged (shown). They hold hold much more distilled water, therefore, they last longer and are better at keeping mold out of your humidor. The green foam-core units seem to be going the way of the dinosaur.