The "Big O" is a 30' circle that you do figure 8's inside of. A friend and I have some exercises set up in an abandoned cul de sac. I have no problem doing 18" figure 8's, the offset cone weave or practically anything else. So today I marked off a 30' circle. Let me tell you, that makes for a really tight fig.8! It ain't no joke! All I can say about it, is it will be a long time before I will be able to finish that exercise.