I saw those. They appear to have a plastic “bubble”, the ones I’m looking for have a metal cap. They are definitely aircraft hardware. Brad
A-A-55628, COMMERCIAL ITEM DESCRIPTION: NUT, PLAIN, CAP, HIGH CROWN UNC-2B AND UNF-2B (03-DEC-1997) [SUPERSEDING MS24680F]
A-A-55628, COMMERCIAL ITEM DESCRIPTION: NUT, PLAIN, CAP, HIGH CROWN UNC-2B AND UNF-2B (03-DEC-1997) [SUPERSEDING MS24680F]., This Commercial Item Description (CID) depicts the requirements for Nut, Plain, Cap, High Crown, coarse or fine threads, Class 2..