A Thestral is a breed of winged horses with a skeletal body, face with reptilian features, and wide, leathery wings that resemble a bat's. They are very rare, and are considered dangerous by the Ministry of Magic.
A dog collar is a piece of material put around the neck of a dog. A collar may be used for control, identification, fashion, or other purposes. Identification tags and medical information are often placed on dog collars. Collars are also useful for controlling a dog manually, as they provide a handle for grabbing.
If you've tried a slip collar but had trouble, this tool may be the solution. I would recommend it for dogs that have trouble on the walk, particularly with pulling. If you place the collar on the lower part of the neck, you are actually helping your dog to pull you around. Watch an Alaskan sled dog pulling a load.