WRITABLE & REWRITABLE: This tag features a rewritable chip that supports writing in 125kHz ID format and HID WG 125kHz format. Ideal for creating new or backup access tags. FREQUENCY: 125kHz; Sensing Distance: 2.5 to 10 cm (1 to 4 inches); Data Storage Life: 10 Years. CHIPS: T5577 chips. These chips are not pre-programmed with an ID number and require writing data before use. Ensure you have a compatible 125kHz RFID writer before purchase. MATERIAL: High-quality copper coil inside. Casing made of ABS plastic. Waterproof design. PACKAGE INCLUDES: 50 pcs key fobs. NOTE: These tags cannot be used directly with RFID locks. Data must be written using a 125kHz RFID card writer prior to use. These are blank tags with no preloaded data. Compatible with most 125kHz RFID writers and copiers. NOT compatible with ONITY systems or Proxmark3 RDV4 devices. CHIP: T5577 (commonly recognized as a reliable rewritable chip) WORKING MODE: Read-write capable suitable for use with 125kHz RFID copiers/duplicators STORAGE CAPACITY: 330 bits (264 free bits available) READING DISTANCE: 0 - 10 cm COLOR: Black MATERIAL: Plastic PACKAGE CONTENTS: 50 x Key Fobs Note: The package includes only the items listed. Other accessories are not included. Note: Lighting effects and display settings may cause slight variations in color between the image and the actual product. Measurement tolerance: +/- 1-3 cm.