Product review (5 stars): Go wickless!
I grew up in a house on a slab.  We set a can in the bottom of each register, filled each with water, and humidified our home (but yes, it takes time to refill.  That was my job, as the kid in the house :->).  Now that I have a basement, I have no place to sit the can.

With these humidifier registers, we harken back to "the old days."  We don't use the wicks, which saves money on replacements. Using just the reservoir in this register doesn't block the airflow.  I'm livin' on that slab, again, but have the other benefits of a basement - ha!

Our purpose: get rid of our noisy floor model humidifier.  We may find we need to supplement with it for our Midwest winters, but that will mean less noise, fewer trips with those big bottles, and less need for the water treatment chemicals.  We're using our reverse osmosis water, right now.  If we find we still need the chemicals, at least it will be drops instead of tablespoons.