Zacro DC221 Dog No Bark Collar for Bark Control 7 Levels Adjustable Sensitivity Control for 15-120 Pounds Dogs, No Harm Warning Beep and Shock Zacro no bark collar stops unwanted barking with progressively increasing warning sounds and harmless static stimulus 7 sensitivity levels (1-7) adjustable for the different size of dogs barking and specific environments through the "+" /"-" button The stimulations repeat through 7 correction levels, the intensity gradually increases until the dog stops for thirty seconds Lightweight receiver, unique bark terminator, effective on a 15-120 pounds dog Adjustable nylon collar senses vibration in dog's throat during barking