Product review (1 stars): Low quality, does not work.
I agree with the earlier review of djmic.

There is a design flaw in the case/battery cover. The battery cover operates as the on/off switch. In order to turn the hygrometer on one lines up the two indicator "bumps". This brings a notch in the cover inline with the contact in the main part of the unit, unfortunately the On position is also the open position, when one turns the unit on, the battery cover is loose and the spring pushes the cover off and the battery out of the unit. It just does not work. I have no comment on accuracy. I have diligently tried to make it work including taping the battery cover in place; it's just not going to work, at all.

I would NOT recommend this item to anyone. I would not purchase this item again.