Most train and transit systems these days accept refillable, RFID travel cards that you buy once and refill electronically anytime they run low. If you're more likely to lose a card than a keyfob, this Instructable shows you how to pull out the chip and mold it into a more travel-friendly accessory.

The guide was posted by Sugru, but actually performed by Jude Pullen, a designer whose work you've seen at Lifehacker before . He uses acetone to melt down the plastic card, remove the RFID chip inside, and press it into Sugru, which he then molds into any form you prefer. By the end, you'll have a keychain that's shaped like whatever you want—even something inconspicuous like a circular keyfob—that lets you use your keys as your travel card instead of fishing for a card to scan every time you enter or leave the subway. RFID Token

If you're planning to do any of the Raspberry Pi hacks we've featured this week, you'll probably…

It's a fun project, but we should note: Not all transit systems will take kindly to you modifying their travel cards. Make sure it's okay with your transit system first (or at least you don't expect help if something goes wrong). Depending on where you live, the reaction could range from "oh, that's cool" to "I don't understand what you did so you're in trouble." Your mileage may vary. That aside, I know I'm definitely more likely to lose a card I take out of my wallet and keep in my pocket than something attached to my keys, so if you're like me at all, it may be worth a shot.

NTAG213 Card Transform Your Oyster Card with Sugru | Instructables