What should be present in each female coupling of a fire hose?

In each female coupling of a fire hose, a pliable rubber gasket is essential because it serves to create a watertight seal when connecting two hoses or fittings. This gasket ensures that water does not leak from the connection, which is crucial for maintaining effective water pressure and flow during firefighting operations. The pliability of the rubber allows it to conform to the surfaces of the couplings, filling any small gaps that may exist and preventing leaks.

While other components like a metal ring, a threaded connector, and a locking mechanism are important in certain contexts, they do not provide the specific function of sealing that the rubber gasket does. The gasket's role is critical for the reliability and safety of firefighting operations, enabling firefighters to maintain the integrity of their water supply under challenging conditions.