PetSafe Elite big dog spray bark control collar is simple to operate. When your dog barks, a burst of citronella scented spray is emitted which dogs find unpleasant. While not harmful it deters excessive barking. Designed to use for dogs weighs 40-pounds and up or up to 28-inch neck size. Patented perfect bark technology ensures only your dog's bark will cause the correction. Waterproof receiver collar. Good/low battery and spray indicator. Collar uses 6-volt alkaline included battery. A unique, patented sensor uses both vibration of the vocal chords and sound sensors (dual detection) to distinguish each bark from other external noises. As he barks, he receives a safe but annoying burst of spray. He will quickly learn the association with this stimulation and stop the unwanted behavior. Their is about 40-50 sprays included in single refill.