Personally I am not a fan of them ever since I got one brand of them and put them on Ajax. It malfunctioned and kept shocking him. In less then a minute it had burned two holes in his neck that became infected. I contacted the company and they did send me compensation and within a month Ajax was all healed up. He had no issues with collars even after the incident so I was lucky there. But after that I am warry to use anything that shocks my dogs.

I am not trying to tell you not to use them. I have and was successful with them until the one that malfunctioned. Just like any training aid they can be a useful tool if used right. I am just saying make sure you get a very well known and reputable brand.