Easy to use and relatively reliable for its price, once you get used to it you can better understand the needle indication which may not be very accurate.

Although its design is not perfect, it successfully accomplishes the task for which it exists, and due to the fact that it does not require cables, batteries, etc. to operate, you will ultimately find yourself using it much more than if you had a multimeter, for example. Not perfect because it could have been made somewhat better so that you don't have to put the battery at an odd angle to measure it. However, this design allows you to even measure batteries that it has not been designed for (as long as they are 1.5V), such as CR2032.

It is small and convenient, it shows you if the battery is new, but it lacked accuracy in the test, you can see if the needle moves quickly and reaches the green, but in borderline cases, it is not easy to understand what is happening, you can clearly see the discharged ones. It also has the other good thing that it does not need a battery to work. For its price, it is fine.

It is very useful and works great.
However, I don't know if it's a coincidence, but I have never seen a medium indication, it either shows the batteries almost empty or almost full.