The Acu-Rite has a tolerance of +/- 5 degrees F. If you have several Ball Pythons it is a good idea to get something on the high end that has a 1 or 2% tolerance as a double checking device. We got a Fluke IR temperature detector (the point and click kind) with a Thermal couple input the thermal couple input is good for 2% tolerance and we stick by each thermometer to varify readings as we get close to the desired temp. When the fluke reaches the desired temp we look at the acu-rite and use the temp on it as a reference only.