I bought this rack from ReptileBasics, it's the four drawer sweater box model. The temperature range is only 2-3 degrees different now between tubs, so I won't worry as much as I was. I think I am going to use probes on all the belly heat tape strips now too, good idea. I have three extra temperature probes sitting around from my old aquarium setup. I have my thermostat heat probe taped to the middle drawers heat tape.