Product review (4 stars): a good bargain but with a couple drawbacks
I purchased one of these and was disappointed that it only displayed in Celsius.  I was directed to a YouTube site that explained how to fix this. It looked easy enough. I watched the video and applied the fix and then determined I didn't know how to put the unit back together again. I decided to buy 2 more units and pay close attention when I took them apart so I could put them back together.  The new ones arrived but they did not have the batteries in the package as the first one I ordered did. There is also nothing on the package stating what kind of batteries it uses. I found the battery type in the Amazon listing, but was disappointed the batteries were not included. I am rating the units a 4 because they are inexpensive and  work.  Also be aware they are made to fit in a 1'x1 3/4"opening. But if you want them to read Fahrenheit you will have to take apart and do a little soldering.