Product review (2 stars): Good Magnets Poorly Attached
I bought a pair of these, and they both worked well, except for one thing.  These come with a strong magnet on the back.  When I received mine, I put them both on my refrigerator for a few days to make sure they were working.  Within 3 days they had both fallen off the refrigerator because the magnet is attached to the back of the units with a piece of double side tape, which is not strong enough to hold the weight of the Humidity Monitor.  Don't buy units for the magnetic mount, unless you are prepared to epoxy the magnets back onto the units when the tape fails.