2 floor vent register air duct sponge humidifiers. Very hard to find! These old-style floor vent sponge humidifiers used to show up in mail order catalogs and they really did the job for keeping dry rooms moist. I just found some in a closet and I'm listing them for folks out there who might be trying to find them. You just wet the sponges inside the plastic frames, which are on little feet so they sit above your floor or carpet, and let the air coming up through your ducts pass through the wet sponges, moisturizing your room. You can even stack one on another for added benefit. A simple concept and sooo much cheaper than mechanical humidifiers. Especially convenient if you don't have enough wall outlets to plug in humidifiers or enough floor space for them, or don't want the noise from them. This listing is for two sponge humidifiers, and I'm listing another two as well. There is a slight bit of rust in some spots and the last photo shows where the sponge is torn a tiny bit, but that does not cause any leaking or any problem whatsoever, and the torn part can just be pushed back into place. Sometimes the simplest (low tech.) solutions are the best.