National Standard Thread, also known as National Hose (NH) thread, is one of the more common couplings used in fire equipment. The male and female straight (non-tapered) threads screw together and the connection is sealed with a gasket.
What is a coupling?
Couplings are sets of connection devices that interconnect to additional lengths of fire hose, adapters and other firefighting appliances. Usually made of stainless steel or aluminium, couplings are available in a variety of types and sizes.