You cannot hold a humidity level you are not measuring. These are the small round gauges that sit inside a jar and read temperature and relative humidity through the glass — six of them, so every container you care about gets one instead of you moving a single meter around and guessing about the rest.
- Reads humidity from 10% to 99% RH, accurate to about ±3%
- Reads temperature from -58°F to 158°F, accurate to about ±2°F
- Refreshes every 10 seconds
- Small enough to drop into a standard mason jar and still read the display from outside
- Six units, batteries included
- 4.5 stars across 1,700+ Amazon reviews
Why we picked it: this is the cheapest thing in the shop that changes how you store. Put one in a jar next to a 62% pack and you will find out within a day whether your container actually seals — most do not, and until you measure it you have no way of knowing.
