They have a super wide nose bridge (because dogs have really big noses) and unique three strap system that keep the lenses away from the dogs eyes and out on the bridge of the nose where they belong. Dont let the lenses of ordinary sunglasses touch your dogs eyes it could cause serious damage. With K9 Optix youll be the coolest dog in town (and the safest!) These will make any canine companion look cool! So super stylish you might just want to keep them for yourself. They are the essential accessory for every fashionable canine! Features:Soft elastic adjustable head and chin straps100% UV protectionAnti-fogShatterproof SIZE CHARTExtra Small Dog Size: 1 - 10 lbs Head Strap and Frame: 5 - 13 inches Chin Strap: 3 - 7 in Breed example: Chihuahua Pom Small Dog Size: 9 - 25 lbs Head Strap and Frame: 12 - 20 inches Chin Strap: 4 - 8 inches Breed example: Beagle Westie Medium Dog Size: 20 - 60 lbs Head Strap and Frame: 15 - 25 inches Chin Strap: 5 - 11 inches Breed example: Dalmation Border Collie Large Dog Size: 50 - 100 lbs Head Strap and Frame: 18 - 30 inches Chin Strap: 6 - 15 inches Breed example: German Shepherd Labrador Retriever Large Dog Size: 100+ lbs Head Strap and Frame: 22 - 45 inches Chin Strap: 11 - 26 inches Breed example: Large Rottweiler St. Bernard