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 5920-00-490-1226
NSN 5930-01-268-7774
NSN 5998-00-004-2694
NSN 5925-01-276-3749
NSN 5925-01-303-0932
NSN 6650-00-295-3524
NSN 6650-01-381-2972
NSN 5855-01-267-2751
NSN 6130-01-400-6123
NSN 6240-01-292-7858
NSN 6685-00-213-1475
NSN 5950-01-052-1856