These use an NTAG chipset, a 'Type 2' tag usable with any smartphone. Unlike "Classic 1K" cards (a.k.a. MiFare S50s), these tags are more secure and work with almost any phone with RFID support, since they avoid the patent issues with MiFare, which require an NXP chipset or a license fee.

One of each of our favorite 13.56MHz RFID/NFC NTAG2x3 tags - 5 in total!

• 13.56MHz RFID/NFC Clear Tag - NTAG203 Chip
• 13.56MHz RFID/NFC White Tag - NTAG203 Chip
• 13.56MHz RFID/NFC Clear Keychain Fob - NTAG213 Chip
• 13.56MHz RFID/NFC Sticker - NTAG213 Tag
• 13.56MHz RFID/NFC Card - NTAG213 Chip (credit card size)

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 rewrites. 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.