S: 22X23CM. Neck diameter: 8cm. Neck circumference: 15-23cm M: 27X27CM. Neck diameter: 9cm. Neck circumference: 20-30cm L: 40x40CM. Neck diameter: 13.5cm. Neck circumference: 32-45cm 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 - Inflatable design and the soft outside material will let your dog wear it comfortably and it does not block your pets vision, they can eat, drink, sleep and play normally EASY TO STORE - Inflatable recovery collar, you can deflate it and store it in a small space when you do not use it and there is a zipper opening on one side, you can take the bag out and wash the outside cloth ADJUSTABLE - There is a strap on the opening of the collar, you can adjust strap for a perfect fit and put the strap side at the back of your dogs neck in case of biting DURABLE AND STABLE - The premium protective collar is soft and washable, it will not mark or scrape furniture and you can insert your pets everyday collar through the inner ring loops for a stabilization. Measurement differences may exist.recommended size is just a suggestion NOT a guarantee in fit as every dog is different.