What is this for?
I don’t know either…
Flash deals are pulled from Amazon overstock. Our features and photos contain all the info that was available on Amazon. You might take a swing at google to see if the more info is out in the interwebs. 
This will control a furnace that has different zones, for ex.: an office area, or a very large house. That copper part goes inside ductwork or maybe some other enclosed area where you want to measure and control the temp.
This could easily be adapted by a home brewer to control a refrigerator or freezer to maintain proper temp during fermentation. I’m definitely going to consider this one.