Yeah it's suctioned right above the UTH on the bottom of the glass. I was afraid to turn it up on high because it seems like no matter where I set the dial it functions at full blast. A family member who raises snakes suggested placing the probe on the inside of the tank under the hide for a more accurate reading. He stated that it's probably 10 degees cooler inside. I have about 2 inches of aspen bedding down so I hope that between that and the glass a lot of the heat is absorbed before reaching Diablo.