The ideal length for the jo staff. The jo which is shorter than the bo and from what I know, generally speaking, 6 feet is the cutoff point. If your staff is 6 feet or longer its a bo, if its shorter than that its a bo. Anyway, the ideal length for the jo depending on the person's size, I read that when you place the bo up and down with one end on the ground the other end should come up to your armpit. So depending on how tall you are that's how long your jo should be although Im not sure how steadfast this rule is. In some ways, it seems a bit long.