These tags works in the 125 kHz RF range. These tagse out with a unique 32-bit ID and are not re-programmable. These EM4001 also know as GK4001 or TK4001 tag and alsopatible with EM4102 tags . We also provide printing and encoding facility for all kinds of RFID cards, tags, keyfobs, wristbands, etc.. please contact us for pricing.These are also backwardpatible with T5567 and T55x7. These key fob tags operate at 125kHz. The Proxmark3, iCopy2 or iCopy3 can be used to program these tags. Contactless Read/Write Data Transmission. Radio Frequency from 100kHz to 150KHzuding 32-bit Password. Separate 64-bit memory for Traceability Data.T5577 Proximity RFID Keyfob is a low frequency 125KHz access key cards, 40.38*31.5mm, 35.5*28mm, 51.5*32mm or customized dimensions we …LF 125KHz tk4100/T5577 RFID PVC Keychain Fob for ID Identification Door Locks. This is a 125KHz keychain which can be repeatedly copied, erased and written. Also can work with 125kHZ HID cards. It can be written with an ID number too. You can use it for door access, elevator access, parking and other fields.