A pocket pistol is an American term for any small, pocket-size semi-automatic pistol or, less-popular, any other handgun (e.g., derringer, or small revolver) of (most commonly) small caliber, suitable for concealed carry in either a front or rear pocket of a pair of trousers, or in an exterior coat pocket. Some consider the term solely applicable for hammerless handguns that are striker-fired in semi-automatic blowback configurations, only. However, with the advent of newer and smaller double action only (DAO) semi-automatic pistol designs, some locked breech concealed-hammer pistol designs are now also called pocket pistols. Well-made, more-expensive pocket pistols are called mouseguns.