I bought 5 of these cards!
I have them in my wallet, passport case, briefcase, carry-on and car.
I used to buy Apple AirTags but these are much better: sleek, not bulky, black (=discrete) and most importantly... rechargeable. A single charge takes a few minutes and lasts 4 months.
On top of that, the volume of the tracking beep is loud and clear.
Last year I happened to drop my wallet in the internal mechanism of a business class seat: I was confident that the AirTag was going to help me find it... unfortunately the beep was so faint that it could be barely heard.
It took me and a United technician approximately 10 minutes to figure out where the wallet was. I wish I had an Ekster Finder Card... we would have found it immediately.