I have two very large breed Italian Cane Corso pups over a 100 lbs and they were always barking at the neighbors. So I got the collars and set the vibration on high at 6, the shock at medium on 4 and the sensitivity at medium on 4. It worked fast but they still barked but only once or twice at first. I have tried the shock on my self at 4 and it was like the trick gum zapper. Anyway it's been a month now and working great. Now I have turned off the shock and left the rest the settings the same with good results. Would recommend.