Since courses need to be customized for different sizes of dogs, unique configurations of obstacles are set up based on the individual height class that the dog is in (you certainly wouldn't want a Chihuahua and a Great Dane running the same course!) (goodpetparent.com)
Beagles compete in one of two different height classes: Beagles 13 inches tall and under compete in the 13 inch class and Beagles between 13 and 15 inches tall compete in the 15 inch class. (dogtime.com)