Material is brass (copper alloy is the same thing), but the field is having problems with material definition.
A one-piece metal item, usually tubular, flanged at one end, the other end open. It is used primarily for lining and reinforcing the edges of holes. The unflanged end is designed to be inserted through a hole and crimped to form a mating flange. Excludes grommet, metallic and eyelets which are components of pushbutton, turnbutton and turnlock type fastners.
Classification: Hooks, eyes and eyelets, of base metal
NSN 6110-01-442-5601
NSN 6130-01-106-2923
NSN 5960-01-144-9183
NSN 6645-01-353-9786
NSN 5935-01-398-9899
NSN 5999-00-988-3007
NSN 5835-01-566-5462
NSN 6645-01-600-5653
NSN 6110-01-390-0537
NSN 6610-01-500-5046
NSN 6240-01-444-7785
NSN 6150-00-419-5133