Used to replace a burned out box fan that has had its fan blade loose, binding and causing the original fan opened. Looks good and the specs are the same. In fact, unless it overheats and explodes, you can't be sure it's fully functional. I'm pretty sure it works as it should. You'll find these things in small electrical appliances, motors, coffee makers, etc. You need to make sure the specs match what you're replacing. Two things are generally important: the temperature at which it opens and the amperage. You also need to install them exactly like the original, since its position is important to detect heat in the right place. depends on the temperature. You must have some basic electrical skills to replace them as they are usually soldered in place. If you're not careful you can explode them while soldering if they get too hot. That's probably too much for the average person working with DYI. But if you know what you're doing, they're pretty easy to replace. This is a safety device, make sure you know what you are doing and understand how it works before attempting to replace it. You also need to have a good explanation as to why the original blew up and be able to troubleshoot that original cause, otherwise you'll likely just mess up the replacement. There are a few things you can do wrong if you don't understand these devices, and you could potentially disable the security feature originally designed.