I have it - and honestly, it doesn't work very well for me - has a variance of 11%. Like Shelby mentioned, do the salt test .

Otherwise, if you haven't been introduced, do a search on the board for "heartfelt beads" or "viper beads" - keeps the humidity at 65% (+/-), no muss, no fuss. Like a lot of folks here, we don't even check or keep our hygrometers anymore as a result.

Good luck.