That is a half choke, or modified martingale. I know they sell them at PetsMart because that is where I bought Ginger's. They are good for dogs that like to slip their leads (like Ginger ). You can probably find them on the internet as well. It doesn't close completely so it doesn't pinch the dog. I don't know that it will do much for a puller, but it might. If you try it let me know.