Product review (3 stars): Cheap little meter
I bought three of these, and none of them agree with the others.  They'll be off by 2-3 and a few percent humidity.  They ALL read "high" humidity in the 30-40% range, one will only switch to "low" when RH drops down into the teens.  I sat them in the exhaust of my dehumidifier once the house was at ~35% and turned the dehumidifier to constant on, so I know they should have been reading "low".  Good enough for my purposes, I don't really care if it's 67 or 68.  Not bad for the price, but they could certainly be better.