Prong collars are known as “power steering” for strong dogs. Labradors are famous for pulling their owners and some owners and their dogs really benefit from using such a collar. They aren’t as awful as they look - put one on your arm and jerk it and you’ll see it’s not agonizing.
That dog’s prong collar is far too low on his neck. Leerburg has an article that shows how to fit a prong collar on a dog correctly:
http://leerburg.com/fit-prong.htm
I’ve been told that the owner/trainer
doesn’t pull/jerk on the lead while using the collar
rather the dog pulling is what activates the collar.