Two years ago we adopted a dog from the SPCA. He has been great except for the fact that when he is in our house, he assumes that he is the alpha dog and will not listen to anything we tell him. If we go to grab his collar to pull him away from something he shouldn't be into, he snarls and shows his teeth. My biggest fear was that this would escalate to the point where he would be aggressive and bite people. After almost 2 years of trying everything with this dog, I did a lot of thinking and a lot of research and bought this collar. We have only had it for 3 days and it is already turning things around. All I have ever wanted was to get him to the point where he would listen, instead of just ignoring us and continuing to do what he wants. For the first time since we brought him home, he is coming when he is called, and he stops what he is doing when he is told no. And this is only after 3 days of about 4 short (10 minute long) training sessions, and a few other moments where he has needed correction. The first few times we tried the collar, it scared him so badly that he yelped...I did feel pretty badly about this but I realize that the collar does not hurt him. The best part for us is that he doesn't know that the correction is coming from us, so he does not become aggressive when corrected. We had been thinking about giving up our dog before and now I don't think that we will have to. This product was well worth our money for finally getting through to a very stubborn dog.