I bought this mainly to use in the filament dryer of my 3D printer. I bought the two pack because I plan to leave one of them in the filament dryer permanently and the other can be used for other purposes.These come with the batteries already installed so you first have to pop off the back cover to remove a little plastic tab to allow the batteries to work. Once that is done, the display shows the temp and humidity levels. It first comes up in degrees C so you have to press the button on the top of the unit to change the display to F.Once I had the display set to degrees F, I compared the temp and humidity readings to the only other device I have in my house that can show temp and humidity which is an indoor display of my weather instruments and I was pleased to see that they were very close. When I looked at the second unit, the readings were different.I opened the Inkbird app on my phone and it instantly recognized the devices and it was able to display the readings from the sensors. It was through the app that I was able to calibrate the readings on the second sensor. I was also able to rename the sensors through the app so that I could more easily know which was which. I then placed one of the sensors outside and let it sit for a few minutes before I took a reading. I then compared this reading to the weather app on my phone and the readings were very close so it seems that these devices are accurate.The next test was to place one of the devices into my 3D Printer dryer box and take a reading. My 3D printer is in my hot Florida garage so knowing when to turn the filament dryer on is important to get good quality prints. It was 89.7 degrees and humidity of 60%. I turned on the filament dryer for two hours and the reading was 104.3 degrees and 43% humidity so that indicated that the filament had dried sufficiently to make some prints. I mounted the hygrometer to the dryer with a piece of double sided tape and it appears that I can leave it in there even while printed. I have done several prints since mounting it with no problems.I have placed the second unit in my attic because I want to get an idea of how hot it gets there so I can compare it to the temperature of the garage ceiling that I can measure with my Inkbird infrared thermometer. I can hopefully then decide if I should add more insulation.In summary I can say that this is a very good unit that can be used in a variety of situations and at a very good price.

I was very frustrated with getting the small Temperature/Hygrometers for 2 important tasks in my growing cycle - When they are germinating young seeds to seedling stage and when curing after a harvest - The ones I had been using were not very accurate and I had to take the device out of its resting place to read it - Opening the curing bag unnecessarily negatively impacts the quality of the cure and opening the propagation box to read the temp/hum can dry out the young seedlings - I bought this and they are fantastic - Not only are they more accurate, but they are bluetooth and the app gives me more information than I anticipated like VPD which is very valuable in the growing phases,, I do not have to touch or even see the device once I place it as I can read everything on the app remotely from anywhere.. It has already identified a heating problem I needed to fix and shown me some ways to get my vpd under better control. I have several INKBIRD Products and they are all excellent and working after many years of abuse. I am going to purchase a few more so I can use them in my next harvest in my KureBags... A+++++++ ALL-THE-WAY

Seems to be pretty accurate. Thumbs up.

The packaging was very professional and I could not believe the size of the box, at first I thought I only ordered one, but there were two in that box. The size is very compact but easy to read, in the day light, night time, not so much. It would have been nice if there was some sort of back lighting.Next I removed the instruction booklet, again, small but not terribly hard to read. The units you get come with everything needed to get started, batteries are already in place, I then opened the backs on the units and removed the little insulating tab from the battery and then closed the back cover on the units. That fired up the units and quickly the temperature, humidity and other indicators came to life.To switch from C° to F° was a simple press of the button on top of the Thermo-Hygrometer. It has a Min-Max fiction but I found this a little annoying, a fast constant back and forth of the high and then the low, a preference to either slow this down or eliminate it all together would be recommended. By the way, a long press on the button on the top resets the Min-Max, if that’s important to you.There is a keyhole slot on the back to hang the units on the wall or you can use the kickstand on the back to set them at an angle on a flat surface or using neither and the unit sits flat on a flat surface like a desk.Next I opened up the Inkbird app on the iPhone and did a search for the new product. Once I found the ITH-13-B the app recognized the two unites and they were now available in the Inkbird app. It took me longer to find the Thermo-Hygrometer in the vast amount of products on the device page than the install of the product.I then customized the name on both unites and lucky for me I did not have to calibrate the temperature on either altho one did require that I adjust the humidity. I calibrated the two unites with a know accurate device for the temperature and humidity. As I was doing the setup a window popped up that a firmware update was available going from 1.1.1 to 1.1.2 and that also can be found by selecting the setup gear icon at the top right of the app then go to the bottom of that page where you will see “Firmware version >” .The Temperature and Relative Humidity charts are 1 hour, 1 Day, 1 Week are easy to read and color coded, but in the short time I have had these units the 1 Month and 1 Year charts did not change from the 1 Week. I assume after a month and a year the charts will start to make sense. I didn’t bother with the Dew Point and VPD on that same page.It will be interesting to see how long the batteries last, according to the description on Amazon they should lat 8 months, time will tell.I would recommend these units for anyone wanting to monitor the temperature and humidity of various rooms, or maybe other locations like in 3D printers, humidors, greenhouse, the possibilities are endless.