WRITABLE & REWRITABLE: This rewritable chip supports writing in 125kHz ID format and HID WG 125kHz format. Suitable for creating and backup tags. FREQUENCY: 125kHz; Sensing Distance: 2.5 to 10 cm (1 to 4 inches); Data Storage Life: 10 Years. CHIPS: T5577 chips, which are not pre-programmed with an ID number. You must write an ID to the chip before use. Ensure you have a compatible 125kHz RFID 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 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. CHIP: ATMEL T5577 (a reliable rewritable chip). Working Mode: Read-write capable – usable with 125kHz RFID card copiers/duplicators. Storage Capacity: 330 bits (264 free bits available). Reading distance: 0 - 10 cm. Please note that the chip requires programming before it can be read. Color: Black. Material: Plastic. Package Contents: 50 x Key Fobs. Only the items listed are included; other accessories are not part of the package. Note: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement error allowance: +/- 1-3 cm.