PetSafe® brand is here to help you and your pet live happy together™. Keep the batteries in your pet's collar fresh by keeping replacements on hand. This package contains two 6 volt RFA-67 lithium metal replacement batteries. RFA-67 batteries work with PetSafe® bark collars plus in-ground & wireless fence receiver collar systems.  The battery modules are waterproof and long-lasting, lasting 1-3 months, depending on use.