Helmet size chart: S: head circumference 26cm, diameter 9cm, height 5cm, adjustable strap 17-22cm; M: head circumference 32cm, diameter 11cm, height 6cm, adjustable strap 20-26cm; L: head circumference 40cm, diameter 14cm, height 7cm, adjustable strap 25-37cm; Cool look for small dogs. A helmet and goggles set made especially for puppies. With it, you can easily dress your pet up in a different way and make it look cool. It is suitable for small dogs or cats such as Teddy, Pomeranian, Bichon, Chihuahua, Yorkshire Terrier, Pug, Corgi, Maltese, etc. Good protection. The motorcycle helmet for dogs is made of high-quality ABS material, sturdy and durable to protect your dog's head. With hard lenses, dog sunglasses are sturdy and durable, helping reduce UV exposure to your dog's eyes. Adjustable strap. Both the goggles and helmet feature adjustable straps that can be customized to fit your pet’s size. Cool dog helmets and glasses are suitable for many occasions such as outdoors, hiking, traveling, picnics, outings, amusement parks, photography, Christmas, and costume parties.