Connect these fittings to fire hydrants and washdown equipment. Made of brass, they have good corrosion resistance. Some have a hex in the middle so you can tighten them with a wrench.NH/NST (National Hose/National Standard) threads are only compatible with other NH/NST threads. BIT (British Instantaneous Thread) threads are commonly used in the United Kingdom, Ireland, India, Hong Kong, and parts of Canada. They’re also known as John Morris couplings.