Typical Chinese construction, it has the same behavior as all Chinese products in its category. It "waves" in measurement (which under normal conditions means a problem for someone presenting oxygen fluctuation). One second it shows 92 or 93 and the next 97 or 98.
In parallel measurement with a good quality oximeter, this fluctuation does not appear.
You can get an idea, but it cannot be considered reliable.

The product is cheaply made, although it is an economical oximeter. The negative aspect was that while it seemed to work and recognize the finger, it never gave a measurement.

I had bought it in the spring, at the beginning of the pandemic. It hasn't given me any issues and works perfectly. It reads just fine and in a relatively good time. For example, when I'm on the treadmill and I put it on every few minutes to check my heart rate, it reads normally even though I'm running at that moment.

Very good for its price. We compared it to one bought from a pharmacy at twice the price and the indications were not different. I highly recommend it.