This is the UID changeable Mifare Classic 4k size key fob.
The UID can be modified ONLY with an external device (ACR122U, Proxmark3 X and iCopy-X devices).
The UID cannot be changed with NFC on Android or iOS devices.
Command to Change UID
By Proxmark3 X or iCopy-XS
hf mf gen3uid --uid 11223344556677
Windows Program Download Link: PCSC_Mifare_Secure.
Notice: Google Drive may recognize the PCSC Mifare Secure program as a virus cause it can detect the USB devices which it’s necessary to connect the reader. Absolutely it’s a clean and powerful program. Download the zip file with the browser on PC.