This base is designed to hold 25mm RFID tags -- such as the popular NTAG215 round sticker type.

They are designed with a Legend of Zelda Triforce theme on one side and with a flat area on the opposite side where you'll stick the RFID tag.

I wanted them to be compact and easy to store. They can also stack on top of each other with a small recessed lip on one side that locks into the rim on the other.