Thank you for your post. Dogs of any breed or size can compete in flyball competitions, and the height of the jumps is determined by the size of the smallest dog. Dogs need to be one year old or older to compete.
To compete in flyball competitions, you need to be part of a flyball club. Many clubs offer training classes, so I recommend that you contact a club in your area for more information on how you can join and enroll your dog in classes.