Frequency: 125KHz; Chip: T5577 (compatible with other universal 125KHz tags). Writable and Rewritable: Erase and write up to 100,000 times. Ideal for creating new tags and backups using a 125KHz RFID card writer/copier. Important: These cannot be directly added to RFID locks. Data must be written using a 125KHz RFID card writer before use. These are blank tags with no pre-loaded data. Writeable with a 125KHz RFID writer/copier; requires an RFID writer. Not an NFC chip; will not work with NFC phones. Specification: New and high quality. Product Name: 2# ID Keyring. Chip Type: T5577 chip. Working Frequency: 125KHZ. Product Size: 35 * 27.5 * 4MM. Working Temperature: -40-55 ℃. Packaging Material: ABS, PVC. Sensing Distance: 2-10 cm (depending on card reader). Scope of Application: access control/attendance/elevator/parking, etc. Product Color: Random. Package Included: 2 pcs.