Frequency: 125KHz; Sensing distance: 1 to 7 cm (0.39 to 2.76 inch); Data storage life: 10 years. Chip: T5577 (compatible with other universal 125KHz tags). | Writable & Rewritable: It can be erased and written 100,000 times. Suitable for making new and back-up tags, with the 125KHz RFID card writer/copier. | You cannot add them to RFID locks directly. You must write data into them by a 125KHz RFID card writer before use. They are blank tags, no data inside. | Can write by 125KHz RFID writer/copier, need to write by RFID writer. Not NFC chip, can't work with NFC phone. | Please note it can't be read before you program the chip, it's original chip. Can work before you write on it.