The Mikki Nylon Muzzle is a tough yet flexible muzzle that allows your dog to pant and bark. It is designed with adjustable straps and a quick-to-fit catch for convenience. Please Note: This muzzle should not be used for strenuous exercise. The following guide provides an example of which dog breeds the muzzles fit and the corresponding noseband measurements: Size 0: Yorkies, Cavalier Spaniels, Miniature Breeds - 10cm Size 1: Whippets, Westies, Jack Russells, Dachshunds - 12cm Size 1XL: Larger Size of 1 - 13cm Size 2: Beagles, Springers, Cockers, Poodles (Std) - 14cm Size 2 XL: Larger Size of 2 - 16cm Size 3: Labradors, GSD, Dobermans, Retrievers - 18.5cm Size 3 XL: Larger Size of 3 - 19.5cm Size 4: Wolfhounds, Great Danes, St. Bernards - 24cm Size 4 XL: Larger Size of 4 - 28.5cm Size 5: Rottweilers, Bull Mastiffs - 21.5cm Size 5 XL: Larger Size of 5 - 26.5cm Size 8: Boxer - 30cm Size 10: Staff, Bull Terriers - 22cm