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.

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.

Got these rfid tags when I needed some stickers instead of keychain pieces, and these worked great. My only issue is that they stand out on my black phone case, but that's on me. They are plasticy on the outside, similar to a dry-erase board, so you can't color them in with a sharpie. The adhesive is great, it's held up quite well since I stuck one on my phone case a few months ago. And it hasn't not worked once. Super convenient when my phone's easier to reach than my wallet when my hands are full.

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.

I used these to make duplicate rfid's for the door at work to put on my phone, much easier than trying to remember where the fob is, I almost always have my phone with me. The adhesive is strong and never had an issue of them falling off.