Small fits 13 to 16.5 inch neck Medium fits 15.5 to 20.5 inch neck Large fits 18 to 25 inch neck X Large 22 to 32 Inch Neck Martingale Collar With Buckle These are great training collars; 1 inch webbing on medium and large. Small uses 3/4 Please do not choose soft pink for the small. I only have hot pink in 3/4. Tired of the dog pulling, well we got the answer. This collar is made to tighten up and turn hard to control dogs. I like this style with the buckle best for control. The Martingale collar is made to tighten up as the dog pulls and quickly realizes you are in control. Very handy for training especially since the dog soon learns that NOT pulling gives him more freedom. I can't watch owners who just allow their dogs to pull them along instead of being in control. We stand behind these and if your not happy just return them for the cost of the merchandise refunded. We try to print a shipping label as quick as possible. Actually shipping can take two days since these are not made until you order them. We do custom work so please let us know any info that will help us with sizing. A measurement around your dogs body will help with body harness. A neck measurement for collars. We are happy to exchange but it is your job to help make sure you buy the right size. We will not pay for shipping on a return for size although we will happily exchange it for you. Thanks Tommy