A 9VOLT battery costs about 3 euros. I foolishly paid 8 euros. The battery was supposed to be sent with a watering timer but was sent separately, hence the cost

Excellent and with a very long duration. I use it in a moisture measuring instrument. I literally forgot when I put it in (a few years ago). It still lasts

The best battery in terms of its efficiency, especially for musical instruments that require a 9-volt battery. I use it in the guitars I have that have active pickups.

The duration is proportional to the use and the device. In some places more, in others less... it's normal. I use them consistently, a stable value and at a very good price.

I had it for 9 months on my guitar with active pickups and they didn't lose their sound. I should note that I changed it because the tension dropped and the sound quality decreased, not because it broke or wore out. Very good!