I found it very helpful. I used one with my rotti-mix as she would bark all night at other dogs barking (lots of them in our old neighborhood). But I also worked with her a great deal - till she understood "Hush, no bark" and "Good girl, no bark" and so on. Eventually she wouldn't bark as soon as I put it on her, even when it wasn't turned on. I only used it at night, and like I said, worked on behavioral training too. Ours had three levels, a mild buzz, then a little stronger, then stronger - don't think she ever barked more than 2x and never yelped. I have also loaned it to my friend for her barking GSD to help train him, she said it worked well.