Pistol Postol Pilots is designed so that the springs are always under compression, even when fully extended. Volume is used to adjust the initial position of the band with the weight acting on it. The difference between the fully extended volume and the length compressed by the weight is called "total sag" or "damp sag". Total sag is set to optimize the initial position of the volume to avoid bottoming out or topping out under normal conditions. "Bottoming out" occurs when air is added or released, and vice versa.
