We know that bright sunlight can cause discomfort for our eyes, so most of us wear sunglasses or a hat on sunny days to avoid squinting and eye damage. The same is true for dogs; light sensitivity is especially common in dogs with blue and light-colored eyes and a little shade can go a long way to make them more comfortable outdoors.
| Size | Tiny | XXS | XS | Small | Medium | Large |
| Bill Width |  |
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| Head Width | 2.5 to 3.25 inches | 3 to 3.75 inches | 3.5 to 4.25 inches | 4 to 5 inches | 4.5 to 5.75 inches | 5.5 to 6.25 inches |
| Neck Size | 8 to 10 inches | 10 to 12 inches | 12 to 15 inches | 14 to 16 inches | 15 to 18 inches | 17 to 21 inches |
| Approx. Weight | about 5 lbs. | 7 to 14 lbs. | 13 to 25 lbs. | 22 to 45 lbs. | 40 to 65 lbs. | 60 to 100 lbs. |