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. Includes a built-in gasket with a waterproof seal. RFA-67 Replacement Batteries are to be used with many styles of PetSafe® Bark Control and Fence Collars, as well as with the Electronic SmartKeys for the Electronic SmartDoors. Refer to your packaging for proper battery replacement size.