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 are not pre-programmed with an ID number and require data to be written before use. Ensure you have a compatible writer before purchase. 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. Tags are blank and contain no preloaded data. Compatible with 125kHz RFID writers or copiers. Not compatible with ONITY systems or Proxmark3 RDV4. CHIP: ATMEL T5577 (a reliable rewritable chip) Working Mode: Read-write capable – suitable for use with 125kHz RFID card copiers or duplicators Storage Capacity: 330 bits (264 free bits available) Reading Distance: 0 - 10 cm Note: Must be programmed before reading. This is a blank chip. Color: Black Material: Plastic Package Contents: 50 x Key Fob Only the above package content is included; other items are not part of this package. Note: Lighting and display differences may cause slight color variations between the image and actual product. Measurement error allowance: +/- 1-3 cm.