Product review (5 stars): Right on the Money
This requires 4 AA batteries that are not supplied with the units. I bought a pack of AA batteries over at BJs and installed two in the base unit and two in the remote unit. I hung the remote unit on a limb of my Magnolia tree where the sun would not reach it, per the instructions. Checked the back of the base unit to check the F/C setting and opted for F.

Let the units do their thing for a couple of hours and then checked the indoor and outdoor temperatures. They were right on. Great unit.