WRITABLE & REWRITABLE: This rewritable chip supports writing in 125kHz ID format and HID WG 125kHz format. Suitable for creating and backing up tags. FREQUENCY: 125kHz; Sensing Distance: 2.5 to 10 cm (1 to 4 inches); Data Storage Life: 10 Years. CHIPS: T5577 chips. These chips do not have a pre-programmed ID number. You must write an ID to the chip before use. Ensure you have a compatible writer before purchasing. MATERIAL: High-quality copper coil inside. Casing made of ABS plastic. Waterproof and durable. Package includes 50 pieces. NOTE: These tags cannot be used directly with RFID locks. Data must be written using a 125kHz RFID card writer before use. These are blank tags with no preloaded data. Compatible with most 125kHz RFID writers/copiers. Not compatible with ONITY systems or Proxmark3 RDV4. CHIP: ATMEL T5577 WORKING MODE: Read-write capable can be used with 125kHz RFID card copiers/duplicators STORAGE CAPACITY: 330 bits (264 free bits available) READING DISTANCE: 0 - 10 cm NOTE: An ID must be written to the chip before it can be read. COLOR: Black MATERIAL: Plastic PACKAGE CONTENTS: 50 x Key Fobs Note: The package includes only the items listed above. Other products are not included. Note: Lighting reflections and display differences may cause slight variations between the image color and actual product color. Measurement error allowance is +/- 1-3 cm.