Hunter HK-55 Quick Coupling Valve Key for 1.25 Inch Valve Outlet Only. The Hunter HK-55 Quick Coupler Valve Key has a standard 1.25 inch single lug inlet and a one inch male NPT threaded and a three-quarter inch female NPT threaded outlet. The metal handle (shown pointing down) screws into the three-quarter inch female threaded outlet on the key. The Hunter HK-55 Quick Coupler Valve Key is virtually universal and will fit all Hunter, Rainbird, Toro and Buckner standard 1.25 inch outlet brass quick coupler valves.