Suitable for small to medium sized dogs. (Larger dogs better suited to the step-in harness). Adjustable in 2 places, they are soft and comfortable for exercise and so great for swimming and playing in the snow. The perfect choice for active, outdoor loving dogs. Extra Small Neck Size 9-10 inches Extra Small Chest Size 11-13 inches Breed guide Minature breeds, Small puppies Antimicrobial for the protection of the product Special Neoflex material which is kind of like a lightweight wetsuit