1" Female NPT x 3/4" Male Hose Coupling
The HS-1 One inch X Three-Quarter inch Quick Coupling Brass Swivel basically has a one inch female NPT Pipe Thread inlet that screws directly onto a Rainbird, Toro, Hunter or Buckner one inch outlet Quick Coupling Key and HS-1 Swivel also has a standard three-quarter inch male hose thread outlet that allows you to connect any standard three-quarter inch garden hose to the swivel.
The purpose of this swivel is to allow connection of a standard three-quarter inch garden hose onto a one inch Quick Coupling Key.