UID Rewrite Changeable 13.56mhz Smart IC Key Tag Writable Zero 0 Sector 0 Block GEN1 Back up S50 1k Card for ACR122U-A9 Device Copier Clone 10pcs/lot by XCRFID

These are Gen 1 NOT Gen 2 writeable cards. Mifare Classic Tools (MCT) for Android CANNOT write sector 0 on these. I searched for Mifare Classic Tools (MCT) for windows and found Mifare Windows Tool (MWT) which is inspired by MCT but MWT supports Gen 1 cards a well as what I would call 'advanced key retrieval' functionality. ;) With MWT, an ARC122U and a Windows 10 computer these program first time every time. They work great. I was able to backup and copy both the restroom key used at the RV Park I keep my RV in and my datacenter ID badge to access my datacenter. You pick which is more important in an 'emergency' lol either way these worked like a charm.

Excellent value. I've included photos to show the size relative to a US twenty-five cent coin (a "quarter"). Using my caliper, they measure 31.7mm across (1.25 inches), 39.8mm (1.56 inches) from top to bottom, and 3.7mm (0.14 inches) thick. - YES, the ones I received ARE "magic card" UID changeable. - They scan as ISO 14443-3 Type A, MiFare Classic 1k (generic (unknown) chip manufacturer) - They read and can be written to without any issues or errors, including changing the UID using a Flipper Zero and NFC Magic. - Sensitivity is very good, and the door lock reader that I am using them with reads them immediately without issue. I suspect that the negative reviewers claiming they are not UID changeable or witeable either received the wrong item, or those reviewers do not understand how to write the UID or may not understand NFC protocols, or they need a different format from MiFare Classic 1k. Buyers should note that if cloning a lock key, you will need to understand how to decrypt keys and how to collect lock nonces, and not understanding those things is NOT the fault of these, or any other writeable MiFare classic compatible NFC cards/fobs. Special thanks to the reviewer who left the review at https://www.amazon.com/review/R39OBEBNAV9KCF/ref=cm_cr_srp_d_rdp_perm?ie=UTF8&ASIN=B0748DBKW2 . Cracking them open to collect and embed the guts is something that I had not considered, and it is a useful suggestion.

These fobs do not show up as Gen 1a nor can you program the UID on them. I even purchased the ACS122U programmer and this also programmer also failed to write the UID. I was able to sucessfully write other cards with the same sequence. Description is incorrect. They can be used as standard MIFARE 1k cards, just you cannot clone other cards to this one.

Functionality: ​I can confirm the UID is writable & rewritable. I used a Flipper Zero to make a copy and tested it successfully. I posted a screen recording of the Flipper writing to the key. You’ll need the app “NFC Magic” installed. Why did you pick this product vs others?: ​I picked this because I needed the UID to be writable. I’m using a Flipper Zero to copy a key.

They work very well. No Issues!

Used to make copies of a school card, scanned and recognized as Mifare Classic 1Ks. They scan to the reader I got (ACR122U) with no issues and they open doors with absolutely zero delay. The plastic housing feels a little cheap, but you get what you pay for. They do rattle insanely loud and obnoxious if you put them on a keychain. I used some cutters to rip apart the plastic shell, and the coil inside is super thin, so realistically you could fit it inside anything for NFC purposes (e.g. phone/earbuds case). Will be buying again once I've used them all.

Worked great!

These are Block 0 writeable with a proxmark. These are a gen 1 so they will not be writeable with a cell phone NFC. If you are looking to write with a phone, look for a Gen 2. Great fobs for duplicating your Mifare 1K cards. Very thin.