XS: neck circumference 16-21cm, diameter 29cm S: neck circumference 20-25cm, diameter 30cm M: neck circumference 25-30cm, diameter 36cm L: neck circumference 28-34cm, diameter 41cm XL: neck circumference 34-42cm, diameter 44cm 2XL: neck circumference 42-49cm, diameter 54cm Multi-size for Pets: Our dog cones have 6 sizes for XS,S,M, L,XL and XXL dogs. Please measure the head circumference of your pets before purchasing. If you feel like your pet is in between sizes, choose the bigger one. Scratch and Bite Resistant: The inflatable collar is designed to protect your pets from injuries, rashes and post surgery wounds, it will prevent pets from biting and licking their injured area or surgical site and promote recovering from surgery or wounds. Comfortable & Adjustable: The noise-free lightweight microfiber cotton will protect your pet from getting irritated when and while wearing the collar. Also, the collar can work as a comfy cushion for your pet to sleep soundly.