Thank you Voodoo. It looks horrendous and I think I'd rather my dog pulled.
Surely there are far better ways to train not to pull? It looks as though if a dog persists it could do damage? In my experience a Basenji with strong prey drive who sights prey would pull on the leash to get there despite any pain.
Those collars look quite medieval, but they look worse than they are. They can cause far less damage than a regular slip (choke) collarnot only because they're limited slip but because they apply even pressure all the way around the neck, not in one place on the neck as does a slip collar.
They don't work by causing pain. Those prongs don't jab into their necks, turn the collar inside out (prongs pointing out), it'll still work, it works because it applies even pressure around the neck, sort of how mommy dog disciplines baby dog. It's like power steering for your dog, it take very little strength to be effective, that's why many service dogs wear them.