When I first received this CO2 monitor I was impressed with the packaging. The quality of the packaging was what you would expect from high-end electronics. It came with the USB cable needed to get it hooked up, but you'll need to use your own USB adapter, which I'm sure most people have plenty of. After charging it I followed the steps to calibrate which was easy. I have no other way to check my CO2 levels but I have to say I trust it after calibration. The temperature and humidity readings match what is listed on my home's thermostat. If I stand near the device, the CO2 level increases, if I pick up the device and breathe into the device, the CO2 level rises very, very high, if I take the device outside, the reading drops , and after being away from home all day, the reading is back is deeper. All of this is exactly what you would expect. It has only a few buttons for the basic functions of turning the alarm on and off, changing the temperature scale from Celsius to Fahrenheit, turning the device on/off and turning off the backlight. My only criticism of the device is that it only lasts about 24 hours without a battery with the backlight always on. So if you want to keep it always on to measure CO2, it needs to be plugged in or charged daily. The backlight is fairly bright, which is great in a well-lit area, but a bit too bright in a dark room, in my opinion. If you need to know your CO2 levels (I was just considering putting an HRV in my home's air conditioner should be fitted), this unit is easy to set up and CO2 readings are incredibly easy. It worked perfectly for my needs.