Ruffwear Knot-a-Collar Color: Red Size: M (36–51cm) Rope Diameter (M, L common): Approximately 7mm Please check if your dog's head size is 50cm or less. Used a little and then stored at home, so please understand. [Product Information] ・Durable design based on climbing rope ・Slim and simple appearance, yet durable and reliable ・Reflective material for safe night walks ・Lightweight and designed to reduce the burden on your dog