A blank MiFare Classic silicone bracelet - often used for parties/events or identification but also found in other systems where a small proximity card is desired. The bracelet contains a NXP S50 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 MiFare cards as there are a few other encoding standards (like FeLica). These chips can be written to & store up to 1 KB of data in writable EEPROM divided into banks, and can handle over 100,000 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.