Why are there TWO rings in the set? Is one of them the spare?

No. The second isn’t the spare. PULLER was specifically created as a set of two rings. Working with two rings at the same time, the dog and its owner maintain constant contact during the class. However, the dog is used to switch quickly from one object to another (from one task to another) at a high rate of work, which in turn creates the foundation for any subsequent training programs. By using both rings at the same time, you can increase the efficiency of your practice by keeping your dog’s interest in it all the time.