An expandable baton (also referred to as collapsible baton, telescopic baton, tactical baton, spring cosh, ASP, etc.) is typically composed of a cylindrical outer shaft containing telescoping inner shafts (typically 2 or 3, depending on the design) that lock into each other when expanded. The shafts are usually made of steel, but lightweight baton models may have their shafts made from other materials such as aluminium alloy. Expandable baton is one of modern weapons, with which one can defend oneself effectively. They are not only for self-defense, but are also used by security and armed forces.