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 2925-01-607-7754
NSN 5945-01-464-4668
NSN 5835-01-296-3790
NSN 6240-01-442-9923
NSN 5985-01-428-2538
NSN 5990-00-653-8595
NSN 6135-00-519-1325
NSN 6220-00-864-4891
NSN 6685-00-273-7017
NSN 5999-00-468-3753
NSN 6650-01-158-6577
NSN 6135-01-412-8929