Product review (4 stars): Good value
We bought two.  I'm pleased with his little hygro.  I thought it would be bigger, but smaller is better in all regards, except possibly display size.  The display is not lit, so you have to have enough light to read the display.  It seems well made and sturdy enough for an inexpensive plastic little thingy like this. I saw other hygros with min/ max for the last 24 hours.  On this one min/max readings are held until you turn it off and back on.  I don't have any way to verify accuracy but I don't think I need super accuracy for my uke cases.
Another reviewer expressed concern about breaking the removable battery tray.  I was also a bit worried about that.  It would be good to have a clear indicator as to which way to put it back in.  I was afraid it would break if I put it in the wrong way.  I looked inside at the battery connections to figure out which way was up and it goes in pretty smoothly that way.  For this review I tried it upside down.  It won't go in the wrong way, unless you really push too hard.  Still, it's kinda hard to remove and reinsert the battery tray.  That's the only bad thing about it, but it's not a deal-breaker.