I have been a small animal veterinarian since 1986, Texas A&M CVM!
In those nearly 40 years, I have never known of an experienced veterinarian or dog trainer recommending these devices for use on large breed dogs.

Such a device is designed, originally, to allow working dogs, horses, etc to pull a load. Such devices allow for zero control of the head and neck, the part of the dog that most often engages in biting. Please, if you insist on buying such for your large dog for the family photo, be sure to use a leash with a collar around the neck that will not slip off when taking your dog to the veterinarian, to the groomer, or to public places. I know of one fairly large and athletic nurse that was once drug for a significant distance by her Akita as it chased after another dog. She got a serious collar immediately afterward before her wounds even healed.

Note: for a small breed dog less than 20 lbs, the above is not applicable. Small breed dogs are often prone to collapsing tracheas, further traumatized by a collar / leash. At times, owners of small dogs may need to suddenly lift their little dog into their arms as some other person’s larger dog wearing their pricey harness, while dragging their owner, lunges after the tiny dog to mangle or kill it.

That’s enough said. It is sad that so many merchants / advertisers promote these often dangerous devices.

After 40 years and thousands of patients,
Respectfully,

Chris Gleason, DVM