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 6320-01-064-0372
NSN 2925-00-159-9003
NSN 5905-00-711-8566
NSN 5935-00-153-3130
NSN 6610-00-227-8846
NSN 5965-01-335-6630
NSN 5895-01-284-7278
NSN 5998-01-451-4690
NSN 6320-00-004-9158
NSN 5935-00-937-8325
NSN 7035-01-200-4751
NSN 6105-01-095-6807