This is very interesting, so the fences will not work on certain dogs or races but will on more calm dogs. Im sure it will not work on fast dogs, like dobermann wich is fast and just will get the shock for a couple of seconds, what about rottweiler wich is more calm in movement but has a bad temperament when it sees something he doenst like. It would be nice, if people post the races wich will just cross over the fence and the ones that respect it. Im sure the fence will also not work so well on an older dogs, its better if you start the training when he still is young.