How odd-I've seen the trainers in my classes tighten the gentle leader enough so the dog can't open it's mouth wide enough to take a chunk out of someone-can still snap I guess, and drink and pant. I use the halti that only tightens when pressure is exerted on the nose strap. Both are really effective in controlling a puller. On most of my guys I use a greyhound collar (humane choke) because they are difficult for the dogs to slip out of.