Product review (5 stars): Small enough for the humidor.
Small enough to live in the humidor so Boveda packs are no longer taken on faith.  If the humidity number dips, I swap out the boveda pack with a freshly charged one, and the spent one goes into a tupperware with a wet paper towel to charge up.  That jumps hum to about 75% and when that number dips the gage goes back to the humidor and the pack goes back into a sealed container for next swap.

Thought about dropping a start for accuracy, but it's well within the stated range.  Expect to use it as a set point.  When the boveda is purportedly keeping things 62%, this one shows 65% and another shows 60%.  In other environments you probably don't need exact... just a ballpark and whether it's going up or down or the same.  So for the price... as long as it's consistently inaccurate, and I believe it to be from my testing, then you're good to go.  Mostly linear offset where it'll read a couple % high or low from 20% to 100%