It doesn't last as long as users describe. I have put it in an airtag and temperature stations and I have already had to replace it within 2 months. They may be old stock but I haven't figured out where the production date is written. The impressive thing is that they are so well sealed that you can't open them by hand at all. Even trying with scissors, it takes more effort than normal. This is troublesome for me but for others it might be a sign of good packaging. I probably won't buy again because they run out quickly for me!