This LIFEPAK CR Plus CHARGE-PAK Replacement Kit contains the following items: One CHARGE-PAK charging unit; two sets of QUIK-PAK pacing/defibrillation/ECG electrode pads; one CHARGE-PAK discharger which is used to safely deplete a used CHARGE-PAK prior to disposal or recycling; and replacement instructions. The LIFEPAK CR Plus AED functions slightly differently from other AEDs; instead of a battery, it uses the CHARGE-PAK battery system which charges an internal, permanent battery inside the AED device. After an AED use or about two years (whichever comes first), the battery charger and electrode pads both need to be replaced.