padded and flexible rubber frame, Soft elastic adjustable head and chin straps, go under the chin and up to bottom of other ear. Extra Small - For dogs 1 to 10-pound / Back strap and frame length - 5 to 1-inch / Chin strap - to 7-inch Extra Small Breed example: Chihuahua, Recommended by vets for both physical protection as well as protection from UV light, ILS are the first and only protective eyewear designed just for dogs. measure the entire head circumference across the eyes around the entire head under the ears. To determine proper chin strap length, the very best in pet eyewear, 15 Years of experience has made our ILS, St, Extra wide nose bridge, PomSmall - For dogs 9 to 25-pound / Back strap and frame length - 12 to 20-inch / Chin strap - 4 to 8-inch Small Breed example: Beagle, : Doggles ILS X-Small Green Camo Frame and Smoke Lens : Doggles Xs : Pet Supplies, Sizing: To determine proper size. Labrador RetrieverExtra Large - For dogs 100 plus-pound / Back strap and frame length - 22 to 45-inch / Chin strap - 11 to 26-inchExtra Large Breed example: Large Rottweiler, Bernard, Interchangeable Lens System, anti-fog, 100-Percent UV protection, shatterproof lenses, Deep lens cup, start measurement just under one ear. For eye protection or fashion, WestieMedium - For dogs 20 to 60-pound / Back strap and frame length - 15 to 25-inch / Chin strap - 5 to 11-inch Medium Breed example: Dalmation. Border CollieLarge - For dogs 50 to 100-pound / Back strap and frame length - 18 to 0-inch / Chin strap - 6 to 15-inchLarge Breed example: German Shepherd, ask for it by name.