This stick on thermometer for hermit crabs is the perfect solution to the guessing game of keeping hermits at a healthy temperature. If they get too cold they will not live long. They must be at a constant warm temperature. this thermometer provides precise temperature readout at all times. It is perfect for the side of the tank that you keep them in. It sticks on and is easy to apply and remove if need be. We were very thrilled to be able to get it straight out of the package and on to the side of the tank. Super easy and what a clever idea.