This is a ring designed with an interior recess that recieves a small form factor RFID chip or other small electronics package. This ring is designed for a 14x14x2.5mm NFC tag (such as this one). The work was initially inspired by Dhani Sutanto's RFID Oyster Ring. Printed with the awesome help of Freeside Atlanta. The ring can be used to provide an access and authentication factor for NFC enabled computers, mobile electronics, door control systems, lockers, safes, cars, payment systems, public transit systems, and other RFID enabled systems. The ring can store passwords and other sensitive information, and act as a personalized replacement for existing NFC based authentication tags. The ring can be used to share and collect identity information in social settings, via NFC read/write capabilities. This application has in mind conferences, maker gatherings, special events, parties, and other large gatherings.The ring bore is designed to be near US ring size 10, to fit fingers about 6.2cm in circumference. Future version will hopefully feature parametric ring sizing via OpenSCAD*. The ring is meant to be 3d printed. With the the ring axis oriented vertically (as in the STL file), it prints with no delamination or need for supports. In practice I had to sand the inside of the ring bore to fit. After sanding, a bit of acetone applied with a brush brought the surface to a smooth and comfortable finish. After printing, secure the tag in the recess. Future versions may have instructions on how to mechanically embed the tag via 3d printing*. I am still sourcing the tag, so I have not tested either of these possibilities. Congratulations, you have an NFC enabled ring! It should be compatible with, for example, android NFC tag apps.