Important Notes:(1)Suitable for small to medium dogs like Corgi, French Bulldog, Shiba Inu, Beagle, Medium-sized Poodle, not suggest for small Chihuahua or Teacup dog. (2)If your dog is less than 15 pounds, size S may be too big for him. (3)In general, pets need take some time getting used to it, you can distract with treats until he is used to wearing cap. SIZE S SIZE M SIZE L Size Chart Small-Helmet head circumference is about 14 inches. Range of strap: 16.5"-18.5", suggest for 17-27 lbs dogs. Medium-Helmet head circumference of about 16 inches. Range of strap: 18.5"-22.5", suggest for 27-44lbs dogs. Large-Helmet head circumference of about 18.5 inches. Range of strap: 22.5"-25", suggest for 44-88lbs dogs. Please measure the proper size of your dog's head and chin before purchasing. Double Hole Design: The helmet top is designed with double holes, which not only play a role in fixing the head and better protect the dog's head, but also release both ears, making your dog more comfortable and breathable to wear. DIY Making: The smooth surface of the dog helmet allows you to put cool or cute stickers on it. You can decorate the helmet with Hero stickers, Halloween or Christmas stickers, etc. Pets will get more adorable to the public at Halloween, New Year party, great for a Halloween costume. Premium Quality: Our dog helmet is made of high-quality ABS material, which is lightweight but sturdy, can be applied for long term use. The brim on the helmet and soft sponge added inside can give your dog's head and eyes the best protection. No matter what breed your pet belong, he/she can find a cool helmet that works for him/her. Customer Reviews Fits my little frenchies head just right! And now I feel better if we fall sideways. We got a medium and it fits his boxed head just right. I like how it fits and lets his ears through. I like how the glasses came with it stay on his face. Sometimes the helmet will ride back a little on his head but that’s probably because I don’t want to tighten it too much. Needed something to protect golden retrievers head from repetitive Barb wire scalping. Sometimes they just don’t learn to DUCK! Super goofy, but works for our needs!