That they can tell eachother anything, and both will have a slighter different view on it. That they can share ex stories and laugh together at what complete idiots they were. That the other is there to give when one of them is going through a rough time with relationships. That the girl can creep him out with “period” stories while the guy will come up with some clever way to gross her out. That they can check eachother out and give an honest opinion, then laugh after. That they can mouth off to a crazy ex girlfriend or ex boyfriend. I love the fact that I do in fact have a best friend that is the opposite sex.