5pcs RFID 125KHz EM4305 Card Writable Tags Keychain Blue No #3 The chipset is EM4305 , which is Writable/Rewrite and can be used in 125KHz RFID card Copier/ Duplicator Only can copy ID number Compatible with all Door Entry system Size: 4.0 x 3.2 x 0.4cm frequency: 125Khz