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 6110-00-389-3167
NSN 5925-00-796-0679
NSN 6105-01-106-2631
NSN 5935-01-125-0727
NSN 2925-01-250-2731
NSN 5925-00-827-4964
NSN 6620-00-248-6950
NSN 6320-00-937-5625
NSN 7035-00-225-6499
NSN 6105-01-254-1137
NSN 5945-00-615-7742
NSN 6685-01-324-4710