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 6620-00-316-2167
NSN 2925-00-508-6032
NSN 5950-01-301-6954
NSN 5925-00-282-2459
NSN 6650-01-642-7911
NSN 6135-01-113-1507
NSN 6685-00-296-0392
NSN 5975-01-121-6412
NSN 5915-01-425-8615
NSN 6110-01-648-6941
NSN 6145-01-430-0099
NSN 5935-01-152-3279