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 5905-00-865-8657
NSN 7035-00-173-2281
NSN 4140-01-271-1918
NSN 6620-01-032-3937
NSN 5950-00-410-9287
NSN 5905-01-541-0346
NSN 5925-00-465-4534
NSN 5950-01-444-1789
NSN 5996-01-544-4682
NSN 5905-01-495-2617
NSN 6610-00-778-7389
NSN 5920-00-479-5254