This one size fits all collar is the humane and painless way to teach your dog to stop barking - without pain, shock or needless trauma. Within 3 -4 weeks your pet will learn that their barking activates the tone. This unit comes with two adjustments. First is the output level, you can control how long of a tone is sounded. Second is the input sensitivity, you can control if a loud bark triggers the unit or a soft bark. Please note the bark control collar is not intended for use as a restraining collar. When using the collar, make sure that the collar is not too tight around the dog's neck. This item takes one 9V battery that is not included. The unit measures in at 3" x 1 3/8" x 1 1/4".