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 5960-01-423-1085
NSN 5905-00-471-6341
NSN 6105-01-518-8943
NSN 6620-01-023-9330
NSN 5999-01-302-3476
NSN 5930-00-470-2885
NSN 5990-00-711-9890
NSN 5998-01-443-4028
NSN 5905-01-292-5024
NSN 5998-01-488-9859
NSN 5965-01-050-8447
NSN 5999-00-243-9820