The PetSafe Little Dog Deluxe Spray Bark Control Collar is custom designed for small dogs up to 26kg. The collar has a unique patented sensor that uses both vibration and sound sensors (patented Dual Detection) to discriminate each bark from other external noises. A burst of all-natural unscented spray is emitted to deter barking only if both the vibration from vocal chords and the sound from the bark match the same criteria. The system includes waterproof adjustable collar (for neck sizes up to 50cm), spray can, battery and operating guide.