The KeepSafe Break-Away Collar is the only collar that has a patented safety buckle that is designed to protect dogs from collar accidents and can be used securely with a leash. Width Fits Small 3/4 in. 3/4" 10" - 14" Medium 3/4 in. 3/4" 13" - 20 " Medium 1 in. 1" 13" - 20" Large 1 in. 1" 17" - 28" How does the Premier KeepSafe Break-Away Collar work? The KeepSafe Break-Away Collar protects a dog from collar strangulation by using a patented safety buckle that releases in emergency situations, such as when a dog is entangled with an object or another dog. The Keep Safe Break Away Collar is available in four sizes and 2 colors; the breaking strength of each safety buckle has been engineered for its corresponding collar size. If a dog's KeepSafe Break-Away Collar becomes entangled, sufficient force is supplied to cause the safety buckle to release, freeing the dog from danger and saving it from possible strangulation. After the collar has released, it can be reattached and used again and again.