Well, it is an nfc tag you can hang on your keys, nothing special.

That said, it has something I have not seen before. Most of these tags pause the print at some point so you can insert the 25mm nfc sticker. This works OK most of the time, but I found that sometimes it is hard to get the sticker on, or the layer after the pause tries to stick to the sticker and it can't or while trying to get the sticker in place the print comes loose from the bed. So what I did is create a 2 part print. 

First you print the 25mm disk and stick the nfc sticker to that and then you print the actual tag. This print will pause at some point and then you can put the 25mm disc into the space in the tag, with the sticker side down. This way, if there is something that wants to stick to the disc it can, it should not try to stick to it as there is some extra space in the print (0.2mm) but it builds in just a little bit of extra security.

Use an app on your phone to ‘program’ the tag for whatever you need and your are ready to go.