CARD-TECH 10PCs EM4305 125Khz RFID Writable Rewrite Proximity ID Token Tag Key Keyfob Card The chipset is EM4305 , which is Writable/Rewrite and can be used in 125KHz RFID card Copier/ Duplicator. Only can copy ID number,Each token pre-programmed with unique ID which is printed on it Compatible with all Door Entry system Each comes with Key ring included No external power required