Product review (1 stars): Don't buy.  Bad factory calibration,  Erratic readings.  Don't waste your money.
Arrived with the temperature setting about 4 degrees off.  No big deal, didn't get it for the temp reading anyway.  Gauged off of a Boveda the humidity started off totally accurate.  This lasted for about a month before the RH reading started to vary inexplicably.  If it were just off a specific amount and held there, I could work with that.  But no, it seems to climb, and dip erratically.  Some changes seem to go along with temperature changes, and others for who knows what reasons...  Not worth even it's low price.