Product review (3 stars): The caliber 4 is definitely the better quality but it costs many times more
Been doing the 24hr salt calibration test with another hygrometer (<a data-hook="product-link-linked" class="a-link-normal" href="/Caliber-IV-Digital-Hygromter-by-Western-Humidor/dp/B00JXOKQVW/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Caliber IV Digital Hygromter by Western Humidor</a>) in the same sealed jar. After about 12 hours the caliber meter has stayed at 76. This one has been up and down from 74 to 81 back to 78 where it has stayed for the last 6-10 hours. Not sure how accurate this is when I see this one fluctuating and the other one staying steady and closer to 75. Since it has not moved for the last 6-10 hours in the jar then I will say that it should work. The caliber 4 is definitely the better quality but it costs many times more. This one seems like it will get the job done once you calibrate it.

Only Celsius on the temperature as well. Doesn't come with batteries. No buttons to adjust.