This is a blank 13.56MHz RFID/NFC Laundry Tag Button with an NTAG213 chip - often used for laundry or garment identification, information sharing, contactless payment, but also found in other systems where a proximity card is desired. The button contains a small RFID chip and an antenna, and is passively powered by the reader/writer when placed a couple inches away.These can be read by almost any 13.56MHz RFID/NFC reader, but make sure it can handle ISO/IEC 14443 Type A cards (the standard NTAG uses) as there are a few other encoding standards (like FeLica).These chips can be written to and store up to 144 bytes of data in writable EEPROM divided into 4 byte banks, and can handle over 10,000 re-writes. You can use our PN532 NFC/RFID breakout board or Adafruit NFC/RFID Shield for Arduino to read and write data to the EEPROM inside the tag. There is also a permanent 7-byte serial number ID burned into the chip that you can use to identify one tag from another - the ID number cannot be changed.