This is a basic VLF RFID Clamshell Card/Tag used for presence sensing, Aceess Control etc. Works in the 125kHz RF range. These tags come with a unique 32-bit ID and are not re-programmable. Card is blank, smooth, and mildly flexible.

RFID Clamshell Card (125kHz) Features: RFID 125KHz Thin RF Card/Tag 

• EM4001 ISO based RFID IC
• 125kHz Carrier
• 2kbps ASK
• Manchester encoding
• 32-bit unique ID
• 64-bit data stream [Header ID Data Parity]