The Choice Of Top Handlers, Trainers & Other Professionals! For safety when working with biting and chewing dogs. With a fully adjustable strap and quick-release buckle, each muzzle is crafted in strong nylon fabric, lined and with chafe-free inner seams for comfort. Muzzle stays in place on dogs, but its a snap for people to remove and replace! **For the most accuracy, measure around the snout just behind the nostrils :** Snouts: Size 0: 4.5" Size 1: 5" Size 2: 5.5" Size 3: 7" Size 4: 8" Size 5: 8 1/4" Size 5XL: 10 1/4" Size 3XL: 10.5" Size 4XL: 10 3/4"