Percussion caps are small metal cups containing a sensitive explosive compound, typically used in firearms. They were developed in the early 19th century to replace the flintlock ignition system, providing a more reliable and quicker way to fire a gun. When struck by the hammer of a firearm, the cap ignites and sends a flame into the gun's main charge, firing the bullet. These caps are primarily associated with muzzle-loading firearms and revolvers. They come in various sizes to fit different types of guns. The introduction of percussion caps significantly improved the efficiency and safety of shooting, leading to their widespread use in military and civilian firearms.