A nut, flat on top and bottom having 6 flat sides. For items which have internal tapered or straight (parallel) pipe threads, specific electrical conduit size designation, and which when installed, provide a method of tightening to lock the connection, see locknut, electrical conduit. See also locknut, tube fitting. For items having a thickness (or height) exceeding two times the width across the flats, use post, electrical-mechanical equipment. (when height or thickness and/or width across the flats is designated as a tolerance dimension, the maximum dimension will be used to determine compliance.)
Dept. of the Army 
Dept. of the Air Force 
Defense Threat Reduction Agency 
U.s. Marine Corps 
Dept. of the Navy 
Federal Aviation Administration 
U.s. Coast Guard 
National Weather Service 
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration 
General Services Administration 
Austria 
Finland 
Lithuania 
Poland 
Brazil 
Spain 
Singapore 
Kuwait 
Morocco 
Malaysia 
Thailand 
Australia 
Belgium 
Canada 
New Zealand 
France 
Germany 
Republic of Korea 
United Kingdom 
Philippines 
Netherlands 
Portugal 
Italy 
Denmark 
Norway 
Greece 
Turkey 
NATO Maintenance and Supply Agency Classification: Nuts of iron or steel
NSN 6105-01-254-6210
NSN 6650-01-497-5782
NSN 5895-01-646-0529
NSN 5960-01-468-6508
NSN 5855-01-233-2767
NSN 5975-01-121-4324
NSN 6130-01-306-8971
NSN 5855-01-228-0942
NSN 2925-01-609-8464
NSN 2925-01-172-0176
NSN 6150-01-268-1967
NSN 5960-01-170-4057