The Standard Bark Collar is the simplest and one of the smallest bark collars available! When your dog barks, this anti-bark collar gives a warning beep and mild correction. Then if he continues to bark, he will receive the warning tone with a slightly stronger correction. This process will continue up through six levels of correction. The collar senses the vibrations in your dog's throat that happen only during barking. While not at all harmful, the Bark Control Collar is an effective deterrent to excessive barking. Note: The image represents both the Deluxe Bark Collar (bottom) and the regular Standard Bark Collar (top). The Deluxe Bark Collar (#PSSBC18) is sold separately.