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 5925-01-522-8369
NSN 5930-00-127-7741
NSN 5945-00-276-9274
NSN 5920-01-101-3360
NSN 6685-01-372-6991
NSN 6645-01-617-3354
NSN 6240-00-351-5659
NSN 5925-00-945-1118
NSN 6645-00-285-8781
NSN 5975-01-445-1632
NSN 6685-01-029-3773
NSN 5990-01-254-3197