It is a valve containing one or more outlets, each with a diameter of 2.5 inches, and it has well-known names, including fire department outlet connection or fire hydrant FH. Military firefighting is for civil defense personnel and trained persons, and may not be used by ordinary individuals. It usually has a 2.5-inch hose made from the book next to it so that the firefighter has it ready to use at the time of a fire.