Measure the widest part of the paw while your dog is standing. Size 1 fits paws 1.10 inches wide for dogs 2.2-6.6 lb Size 2 fits 1.29 inches for 6.6-11.0 lb Size 3 fits 1.49 inches for 11.0-16.5 lb. These soft, breathable booties protect paws from heat, stones, glass, snow, ice, and rain. The skid-proof sole gives steady traction on various surfaces. Reflective straps enhance visibility at night. They also prevent nail damage to floors.