NFC (near field communication) technology is a great way to interact wirelessly with projects. With the RFID/NFC Smart Ring your ring can communicate with your smart phone/tablet, computer, or much more! Contains two MiFare Ultralight C – NTAG 213’s with 144 bytes of read/write memory. One is on the ‘inside’ of the ring towards the palm, the other is underneath the jewel. You can use tags to launch apps, unlock your phone, transmit a URL, control an Arduino, etc.