Each Roger's Connection tube has a magnetic North end, and a magnetic South end. Most of the time, it won't matter which end you use. But sometimes, when you have many tubes connected to the same ball, an unequal concentration of magnetic forces may make it difficult to connect an additional tube - the new tube will "push" away. If that happens, then just use the other end of the new tube that you are connecting. Instead of being difficult to attach, the new tube will be attracted strongly to the ball, because the north and south magnetic forces will be better balanced on the ball.