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 6135-01-167-7604
NSN 5925-00-404-9035
NSN 5965-00-099-0698
NSN 5930-01-562-4298
NSN 5915-01-366-9850
NSN 6220-01-493-9918
NSN 5965-01-476-0721
NSN 6620-00-930-5680
NSN 5975-01-204-1368
NSN 5990-01-123-4226
NSN 5925-01-399-4007
NSN 6105-01-224-5510