well I've got it where there's about a 1/2 gap all the way around and in the middle. I'm doing this because my house is kept cold and its keeping in the warmth pretty well. I tested all tubes 1 by 1 before I'm dropping a snake in, there staying steady at about 90 on warm and 82ish on cold side. what it is is a big like cabinet that was way on sale because it was a display model so it was $60 originally 120. I have fixed it up to make gaps for some ventilation. My snakes seem to be way way more happy in them. Last check of humidity was around 58ish or so.