Flexwatt is a name brand I believe, but it basically is the same thing as a uth. It's basically like the heat mat you buy at a pet store it's just not encased in the rubber or whatever. Also I think it's specifically geared towards reptiles and won't get as hot as some of the matts can. Personally I think I'm just going to go with the RHPs. They are more expensive but just seems like they would work better to me. I figured I would call when I go to order and ask them what they think the best set up is. They don't sell RHPs so it's not like they are trying to make extra money by pushing something you don't need. If you set it up for two snakes you put the flexwatt in the middle. There is actuallay a cut out in the bottom so it sits flush. They also cut a channel for the temp probe. So you might be able to go with the flex watt for the hot side and then an RHP to help with ambient. To me it seems like the uths only work if you use paper towel or newspaper or something really thin as substrate. If you use aspen or cypress or something it seems to be too much of an insulator. But there are a lot of people on here that have them that can tell you more about them. And everyone i've talked to has confirmed that it is big enough for two. A lot of people keep them in tubs. It's counter intuitive to what we think most animals would like, but the truth is these are nocturnal animals that spend a lot of there time in a rodent hole or termite mound. They like small tight spaces that make them feel secure. A lot of people that do tanks keep adults in a 20L vs the 40 that we have.