Dog Collar Bark Stopper Prevent Dog Barking - 2 Units-This innovative collar has seven sensitive levels, used in different types of dogs. When your dog barks, the collar will issue a warning to stop and stop unwanted howling. If your pet continues to bark, the collar will pass through seven levels, gradually exacerbating the stimulus until your dog is quiet for thirty seconds. But do not worry - No-Bark Collar is a completely safe and harmless pet! In order to increase protection, if your dog reaches the seventh level, the collar will stop working for a minute. Because it is suitable for 10-120 pounds of dog, for almost all varieties are very good.