WRITABLE & REWRITABLE: It's rewritable chip, and it can write in 125khz id format and H ID WG 125khz format. Suitable for making and back-up tags. FREQUENCY: 125kHz; Sensing Distance: 2.5 to 10 cm (1 to 4 inch); Data Storage Life: 10 Years. CHIPS: T5577 Chips, it doesn't have pre-programmed id number, so need to write the id on it before you read, so make sure you have the writer before you buy it. MATERIAL: High-Quality copper coil inside. Casing Material is ABS plastic. Waterproof & Durable. Package includes 50Pcs. NOTE: You cannot add them to RFID locks directly. You must write data into them by a 125kHz RFID card writer before use. They are blank tags, no data inside. Can write by 125KHz RFID writer/copier,CAN NOT WORK WITH ONITY SYSTEM and Proxmark3 RDV4. chip: ATMEL T5577 (The best rewritable chip) Working Mode: Read-write modes - Can be used in 125KHz RFID card Copier/ Duplicator Storage Capacity: 330 bit (264 free bit availability) Reading distance is 0 - 10cm Note: Please note it need to write the id on it before you read, it's chip. Colour:Black Material:plastic Package Contents: 50 x Key Fob Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Note: 1. Please allow 1-3 mm error due to manual measurement and 1-3g weight error make sure you don't mind before ordering. 2. Due to the lighting of the photos and the difference of monitors, the pictures may not reflect the actual color of the real item. Please make sure you don't mind before ordering, thank you! About Shipping: 1.please pay attention to your delivery address such as: name, street, house number, doorbell/email without name, etc. is correct, or the order will not be delivered correctly. 2.All items will be shipped within 3 business days after the payment is received. Most times you will receive them within 8-12 days then. The specific delivery time is depend on circumstances. 3.During the shopping process, if you have any questions, please feel free to consult us, we will reply you within 24 hours Hope you have a pleasant shopping experience!