Oops, sorry! Didn't mean to confuse you. I thought you stuck the gadget to the bottom of the cage. Okay, I got this. The thermometer part is what I call the probe. The "outside temp" is that. The inside temp is the temp wherever the gadget is, in this case, the room. The humidity is also measured where the gadget is. Most of the time, the air outside the cage is drier than inside the cage. Place the gadget in the cage, and you'll get correct humidity measurements. If you literally can't fit anything, than maybe the 41 qt would work.
0.1 Super pastel