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 5905-00-410-1766
NSN 6620-01-435-7083
NSN 6220-00-285-8104
NSN 5905-01-100-1146
NSN 5895-01-537-2003
NSN 6150-00-438-1520
NSN 5975-01-407-9234
NSN 5915-01-380-3934
NSN 4140-00-296-9695
NSN 6610-00-105-1665
NSN 5905-01-412-3602
NSN 5905-01-504-0386