1 Inch Width Martingale with Buckle Dog Collars - Heavy Duty Nylon (1" Width Dog Collars If this is your first time ordering from Caninus (K-9-us) Collars, thank you for choosing us for your pups new collar. Please follow these steps to ensure you order the correct size and appropriate width for your pups new collar. All Caninus Collar products are hand made by us in the USA. KNOW THE CIRCUMFERENCE OF YOUR PUPS NECK - If you do not know the circumference of your pups neck please measure it before ordering. Please do not use sizing from another company. Our rule of thumb is that you want to get the circumference of your pups neck as close to the middle of a size range of a collar as possible. Our size chart is broken down by inches. If you need an in between size or a XX-Small please send us a message. We monitor the messages on here and reply pretty fast. SIZING FOR A MARTINGALE COLLAR  When choosing a size, you have to make sure the collar will open up enough to fit over your pups head. Measure your pups neck as well as the widest part of his/her head as well to ensure the collar will open up wide enough to fit over the head. This does not apply to Martingale with Buckle collars because the collar opens from the buckle like a standard side release buckle collar for easy on and off and functions the same as a martingale collar PLEASE FOLLOW OUR SIZING CHART. There is not a standard sizing chart for dog collars. X-Small: 8" - 12" Neck Size // Small: 12"-15" Neck Size // Medium: 14"-18" Neck Size // Large: 17"-24" Neck Size // X-Large: 20"-29" Neck Size //.XX-Large: 28"-34" Neck Size