Petsafe 6 Volt Bm RFA 67 Lithium Battery Dual Pack PetSafe 6 Volt Replacement Batteries easy to use patented design simply locks into place, eliminating the need for tools and easing concerns over stripped screws or difficult installation. Just insert a coin into the slot and twist the battery to the unlock position. RFA-67 Replacement Batteries are to be used with many styles of PetSafe Bark Control and Fence Collars.