ETEKJOY 10 PCS Writable 125kHz RFID Sticker Coin Adhesive Back T5577 Proximity ID Card Token Key Tag Rewritable Dia 25mm (Blank Card No Data)

There are two common standards that I've seen around for doors/garages/offices in the 125kHz frequency: HID and EM4100. The first one has two identifiers facility code (fc) and a card number (cn). The second one is just one number. These cards can be programmed to emulate either of the standards. Programming these cards requires some kind of programming device. I had one old hand-held that can only read EM4100 and is easy to use: push the read button, scan a source card, push the write button and put it next to the writable card. Putting the Etekjoy cards for the writing process successfully duplicates the card and now you have two identical cards. Programming the HID standard (typically the cards that have "HID" embossed on them) requires a reader/writer that understands those, like Proxmark3. If you know the facility code and the card number, the command "lf hid clone -w H10301 --fc 123 --cn 12345" will program these Etekjoy cards and you have a duplicate that will read well in other readers. I really like the small size of the card and the fact that it has a adhesive back. It can be attached to the back of the phone inside a case, for example. The card is not flexible and you have to account for the 1mm width. The cards cannot be read without programming first. Each card being under a dollar is a great value.

Doesn’t work

I purchased these because I got tired of carrying around my key fob. I was trying to minimize my EDC. I figured I always carry my phone so it would be great if I could dump the fob for something I could stick in my phone case. The maintenance guy at my building claimed they could only do the HID brand fobs. So using some equipment my friend had I copied my fob and wrote it to this coin. It worked perfectly. No more fob! My only gripe is these are a tad thick. They won't work in most phone cases. I did manage to get it to work with one of my 3 cases. The adhesive is strong but not strong enough to just stick to the outside of something like a phone that's always in use.

No problem programing the RFID chips for HID-125 Hz protocol. Read test speeds were much faster than I was expecting. I won’t hesitate to buy more of these.

Make sure to check that all of the stickers are writeable. 7 of the 10 tags were empty pieces of plastic. 3 had the t5577. I don't know if this was intentional or not. The working ones work well.