One rung.
3/4" seems to be the standard small campus rung. Good as a traditional low wall angled campus rung.
1.5" offers a fair amount of real estate to grab on to. I like this size as a a challenging rung for beginners. 16 inches wide.
2" is huge. Almost feels like a jug. Big moves on these or fantastic intro campus board rungs in to the world of campus training. This climbing rung is 16 inches wide.