Downtown Pet Supply Martingale Training Collars are designed for maximum durablity against the elements and energetic play. Martingale collars are no choke, no buckle, and great for training. Our beautifully designed collar is made from high density polyester that is double stitched and paired with nickel plated hardware. Please review our sizing chart to find the perfect fit for your dog. When measuring the circumference of your dog's neck, leave enough space to fit one finger between the collar and your dog's neck to ensure comfort. Small: 9"-17", Medium: 11"-20", Large: 14"-24.5", X-Large: 18.5"-34"