The PetSafe Bark Control Collar is the simplest and one of the smallest bark control 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.Features:Training Video makes the system easy to useTraining manual written by a noted animal behavioristOne of the smallest receivers available at only 2.3 ouncesReceiver Size: 1.75 x 1 x 1.25 inchesAdjustable lightweight collar from 6" to 28"Sophisticated microprocessor technology provides a warning beep with the first barkSix levels of progressive correction for stubborn dogsNot too strong for small or timid dogs...yet strong enough for large or st