The PetSafe Spray Bark Collar is designed to help stop nuisance barking and whining with a burst of spray. The sound and vibration of your dog's bark triggers a sensor on the collar, emitting a burst of spray to help stop the unwanted behavior. The collar includes both a citronella & an unscented spray refill cartridge, so you can determine which one works better for your dog. The recyclable refill cartridges are convenient to replace with no mess, and the collar is rechargeable - no batteries required. The collar is designed to fit dogs 8 lb. and up with necks up to 27" in circumference.