Review on 6-Pack Mini Hygrometer Thermometer - Digital LCD Monitor for Humidors, Greenhouse, Garden, 🌡️ Cellar, Cars, Baby Rooms - Fahrenheit or Celsius Meter - Indoor Hygrometer & Thermometer by Eric Teshome

They never worked, they all read different numbers even if they are all in the same pot so I don't think the temp varies on one side of the coffeeshop -cups to another. maybe I just got a bad batch, but when half of them just don't work, you have to wonder how well any of them can really work. So do yourself a favor and stay away. There are a million other versions of it made by other manufacturers, I'm sure there is one worth buying and at least worth more than this one. They can't even be used to weigh down paper.