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 6130-01-631-1570
NSN 5960-01-411-5217
NSN 6620-01-554-3987
NSN 4140-01-634-0330
NSN 5935-01-232-2910
NSN 5960-01-359-6630
NSN 2925-01-179-2648
NSN 5930-01-207-2447
NSN 5945-00-244-1212
NSN 5990-01-264-6512
NSN 6685-01-358-7448
NSN 5935-01-067-1866