These are made from 5/8″ or 11/16″(depending on the color) smooth tubular nylon(Sm-XLarge). The x-small is made of 1/2″ nylon webbing and comes in black, red and royal blue, only. I usually use the 11/16″ for the larger dogs. The wider width of this webbing is more comfortable for the dog, and does not leave permanent marks on the nose, but the control is the same. Guide Dogs for the Blind is now using this type of head halter.
The piece that attaches to the leash, comes from behind the dog’s right ear, therefore the dogs head is not constantly being yanked around. When the dog pulls, the head halter snugs tighter around the nose. When the dog stops pulling the pressure eases up.
Size of the dogs head determines the size of the head halter. Dogs with smaller heads and thinner noses wear a smaller size. (Jack Russell and other dogs of similar size head=Xsmall, Shelties = small, Border Collies and most Aussies= Medium, smaller Labs and Golden Retrievers= Large and Rotties and block headed Labs=Xlarge) These are just approximations.