Warning!!! When you use any thermostat with flexwatt, please note that you will need to tape the reader under the substrate of your choice on the inside of the tub where the heat tape lays. I have always stuck the temp therm. in the middle cage with my snakes. Then one day I smelled burning plastic! The reader was on the cool side of the cage (just from opening and closing it) and so it was trying to heat up the cold side. I have some very nice thermostats and they were not cheap. So just please keep this in mind when you are plugging everything in. I just put it in the middle cage of my rack, tape it right under the substrate, on top of where the flexwatt meets under the tub. Since I have been doing that, no stinky smell and no little burn hole! Oh and make sure empty slots at least have empty totes in them. That can affect the thermostats temp. reading.