PetSafe Outdoor Ultrasonic Bark Deterrent FOR DOGS OF ANY SIZE  uses high-frequency sound that works to reduce excessive bark of dogs within hearing range; for dogs 6 months and older DURABLE AND WEATHERPROOF - designed for outdoor use only UP TO 50 FOOT RANGE - purchase additional units for larger yards LOW BATTERY INDICATOR - uses a replaceable 9-volt alkaline battery (not included) NO BARK GUARANTEE - Some dogs may not be responsive to ultrasonic correction. If this product is not meeting your needs, please contact PetSafe Brand Call, chat or email with our expert PetSafe US-based customer care specialists six days a week; They are waiting to assist you and your pet with your product needs Manufacturers warranty is only valid when purchased from an authorized retailer