After seeing Dhani Sutanto mod his Oyster Card (London transit pass) into a ring, I got excited to try something similar with an CharlieCard (Boston's RFID transit pass). You can dissolve the card in acetone and then remove the RFID antenna and chip inside.
This guide was first published on Jul 29, 2012. It was last updated on Jul 29, 2012.
This page (Overview) was last updated on Jul 15, 2020.