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 6320-01-512-2031
NSN 5960-01-259-3846
NSN 4140-01-234-6610
NSN 5998-01-264-9768
NSN 6130-00-116-4881
NSN 5999-01-282-9035
NSN 5965-01-188-8530
NSN 6220-01-481-3742
NSN 6685-00-080-2110
NSN 5950-00-324-0472
NSN 5996-01-272-2737
NSN 5945-00-494-4876