Accurate, convenient, logs records and has printable reports for each log.I'd give it more than 5 stars if I could. That being said, it could still be improved upon if the device readout was larger and/or brighter, and if there was some sort of summary reporting or graph of historical data. Oh and an alert for heart rate not just O2.I bought this years ago to determine if I had sleep apnea (I don't). It is much more accurate than my Garmin watch as far as O2 saturation readings. After Covid I started monitoringmy daytime O2 and noticed drops that coincided with heart rate spikes from doing nothing more than standing and/or walking around the house. I started to doubt it's accuracy but the clip oximeter was giving the same readings (although slower). Turns out I had POTS (postural orthostatic tachycardia syndrome). The holter monitor and echocardiogram I had a few months ago didn't pick up on it. I even bought a Wellue ring monitor to compare this with and the results are similar. The Wellue does not show the heart rate and O2 side by side though, and the button is hard to get to work, making this model far superior.Now I'm using it daily to warn me when my O2 falls below 90% and I use the alert on my Garmin for when my heart rate accelerates past 100 - then it is time to sit or lie down. If it weren't for this device I'm sure I'd have passed out and face planted by now.