The pictured case was printed years ago, but I believe it was printed using IC3D red ABS. It has stood up to use and abuse incredibly well over the years with nary a scratch. This case is designed to be a very snug fit - there is an opening in the bottom to be able to push the key card back out if necessary. If you don't want quite as snug of a fit, I would recommend upsizing the design 2-5% before printing. As an extra measure of protection, make sure that after you add your key card, you put a lanyard or keyring through the keyring hole at the top. Provided your RFID key card is one of the same types I've encountered (which seem to have a very similar exterior form factor), the hole should line up with the keyring hole on your card and lock the two pieces together.