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 
National Security Agency 
Defense Threat Reduction Agency 
U.s. Marine Corps 
Dept. of the Navy 
Defense Logistics Agency 
Federal Aviation Administration 
U.s. Coast Guard 
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration
National Aeronautics and Space Administration 
Austria 
Finland 
Lithuania 
Poland 
Bulgaria 
Brazil 
Spain 
Columbia 
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 6650-01-607-6888
NSN 5990-00-907-0184
NSN 6135-01-141-4916
NSN 6650-00-555-1061
NSN 5945-01-540-2250
NSN 5915-00-061-3288
NSN 5895-01-650-1028
NSN 6650-01-480-7754
NSN 6220-01-280-5353
NSN 5996-01-320-3055
NSN 5915-00-482-7151
NSN 6105-00-629-7438