4 RFA-67 BATTERIES FOR PETSAFE WIRELESS OR INGROUND DOG FENCE COLLAR RECEIVER 4 REPLACEMENT BATTERIES: Two 6 volt RFA-67 lithium metal replacement batteries included COMPATIBLE COLLARS: Works with bark collar, in-ground and wireless fence receiver collar systems WATERPROOF AND LONG LASTING: Battery modules are waterproof and last 1-3 months, depending on use QUALITY PROMISE: PetSafe brand has been a trusted global leader in pet behavior, containment and lifestyle innovations since 1998 to help keep your pet healthy, safe and happy FREE AND FAST SHIPPING