Product review (3 stars): Also annoying: nowhere does it mention the little black button ...
Generally,  this product works as advertised.  However,  there were no instructions included.  In addition,  there was no included cable  to allow for external humidity readings.  I bought 2 units and while the temp readings were virtually identical,  there was a difference in the humidity readings of 4 percentage points.  Also annoying: nowhere does it mention the little black button on the back which switches the display to Fahrenheit.  You have to lift out the kickstand to access the button.  At this price point,  I decided to keep the units but I wouldn't recommend this item.