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 6320-01-359-3921
NSN 6320-01-481-7322
NSN 6610-01-450-5688
NSN 5975-00-624-6949
NSN 6685-00-248-7716
NSN 6150-01-232-1608
NSN 6620-01-323-6091
NSN 5975-01-025-1613
NSN 5835-00-554-0399
NSN 6620-00-041-3406
NSN 6645-01-271-7583
NSN 5999-01-234-7943