The one with 2 heaters. 306 I believe it is. I run my house pretty cold all the time so I don't need to cool my tank.Did you get the 306 wifi? I liked the 308 since it was able to turn on the fans and/or heater, but they don't make a wifi aquarium version for it. Customer support said you can cut off the metal probe and attach the silicone probe, so it's something I was looking into doing.