Training Tools - Prong Collar

I know I've already posted about the choke chain and this is a variant of that, but I REALLY want to put up a posting about this. For those of you who are not familiar with it, this picture is a prong collar.

The way it fits is it goes around the dog's neck like a choke chain. The martingale will tighten as the dog pulls and the prongs push on the dogs neck. In theory, it is supposed to teach a