☆Safe and Effective to train your dog to stop barking. ☆Audible Mode: creats harsh buzz to stop barking. High and low modes ( high for big dogs, low for small dogs) Dogs quickly learn that their barking causes this irritating sound and stop barking to stop the noise. ☆Ultrasonic Mode: works by sending out an ultrasonic signal that only your dogs can hear when activated by the barking. ☆Adjustable stretch collar to fit different sizes. ☆Free two AG10 button batteries.