Our exclusive hygrometer stash jars fit perfectly into the Large and Extra Large Bzz Box. With a sealable bamboo lid featuring a built-in hygrometer for keeping track of the humidity in the jar. Because the ideal humidity for herbs is between 58 and 62%, when a two-way humidity pack expires, the humidity will fall outside of the desired range. By being able to monitor humidity, you are ensuring the quality of your herbs. We recommend always keeping a two-way humidity pack in your stash jars.