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 5910-00-819-3899
NSN 6130-00-273-1111
NSN 5920-01-561-2075
NSN 6220-01-089-6220
NSN 5930-01-448-4073
NSN 2925-00-288-1394
NSN 6685-01-401-5360
NSN 5925-01-521-3173
NSN 6685-01-508-9936
NSN 7035-01-068-5077
NSN 5895-01-516-1259
NSN 6685-01-162-2259